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Synthroid (Levothyroxine) Side Effects & Adverse Reactions

Synthroid (Levothyroxine) is a synthetic thyroid (T4) hormone commonly administered to treat hypothyroidism (or thyroid deficiency).  It was initially synthesized by British chemists Charles Robert Harington and George Barger in 1927.  As a pharmaceutical, synthroid is among the most prescribed medications in the United States, with upwards of 20 million prescriptions filled for the drug annually.

The World Health Organization regards synthroid as an “essential medicine” or among the most important pharmaceuticals necessary in a basic health system.  Sometimes referred to as L-thyroxine, synthroid functions by mimicking the effects of the endogenous hormone thyroxine (T4) manufactured by the thyroid glands.  This yields favorable metabolic effects via modulation of DNA transcription and protein synthesis.

In addition to treating hypothyroidism, synthroid is commonly prescribed to lower thyroid-stimulating hormone (TSH), thereby: preventing recurrent bouts of thyroid cancer, inhibiting growth of goiters, and managing nodular thyroid disease (lumps on the thyroid gland).  Despite the proven therapeutic efficacy of synthroid for the treatment of thyroid-related conditions, it isn’t devoid of side effects.  Many synthroid users complain of unwanted adverse reactions that may be unavoidable.

Synthroid (Levothyroxine) Side Effects & Adverse Reactions (List)

Below is a list of side effects and adverse reactions associated with synthroid.  Understand that the severity and number of side effects you experience will be subject to individual variation and dose-dependent.  Once synthroid dosage is properly calibrated, severity and/or occurrence of side effects usually subside.  That said, the most commonly reported synthroid side effects include: sweating, hair loss, appetite/weight changes, insomnia, headaches, nervousness/anxiety, and nausea.

Anxiety: Many individuals taking synthroid report increases in anxiety, sometimes to the extent of causing panic attacks.  It is necessary to consider that if an individual is receiving too high of a synthroid dosage, anxiety may ensue.  Excess or abnormally high synthroid intake is capable of inducing hyperthyroidism by increasing neurophysiological arousal, thereby leading to feelings of tension and nervousness.

That said, it is possible that some users may experience anxiety even after the synthroid dosage is calibrated to an optimal level.  Users may report physical symptoms of anxiety such as muscle tension, sweating, and increased heart rate – as well as psychological symptoms such as rumination or obsessive thoughts.  If you’re experiencing severe anxiety and/or panic attacks from your synthroid, talk to your doctor about a dosage adjustment, alternative intervention, and/or concurrent usage of an anxiolytic.

Appetite changes: A common side effect noted by synthroid users is a change in appetite.  Don’t be surprised if your appetite significantly increases and/or decreases when you initially start taking synthroid.  Many users report a significant reduction in appetite when they first begin synthroid treatment.

If you find it difficult to look at food or eat an entire meal, you are not alone.  This appetite reduction may result in a bit of weight loss – a side effect that many individuals prefer.  However, with continued treatment and proper calibration of dosing, a user’s appetite may normalize and the preliminary appetite reduction and accompanying weight loss may subside.

A small percentage of synthroid users may report an upregulation in appetite.  If you feel hungry all day, have more food cravings, and cannot stop eating – it may be a result of the medication.  Anytime appetite increases/decreases are substantial and/or sustained for a prolonged period – they should be discussed with a medical professional.

Bloating: If you feel as if your stomach is always swollen with fluid and/or gas, you may be experiencing synthroid-induced bloating.  Bloating is a side effect reported by many synthroid users, and one that most people can tolerate.  That said, the bloating may be highly uncomfortable and may cause you to appear chubbier and/or larger around the waste than you would like.

Some individuals report that bloating experienced on synthroid is also accompanied by weight gain.  To minimize the likelihood of bloating while taking synthroid, be sure to eat a clean, healthy diet (devoid of processed foods – as these can exacerbate existing bloating).  If the synthroid is causing your stomach to swell significantly (e.g. to the extent that you appear pregnant) and this bloat is interfering with your ability to function – talk to your doctor about potential alternatives.

Blood pressure changes: Manufacturers of synthroid have confirmed that blood pressure changes can occur as an adverse effect of synthroid.  Although not many people notice drastic shifts in blood pressure during treatment, blood pressure should be regularly monitored among synthroid users to ensure that it’s within a normative, healthy range.  Some individuals taking abnormally high dosages of synthroid may experience hypertension – which could lead to serious cardiac and/or health problems.

If prior to taking synthroid you have a history of blood pressure abnormalities, your doctor should be well-informed of these and adjust dosing to mitigate risks of hypertension.  In some cases, synthroid users may necessitate adjuvant treatment with a beta blocker to offset the side effect of hypertension.  The greater the dosage of synthroid you’re taking, the more likely you’ll be to experience hypertension as an adverse reaction.

Brain fog: Although individuals suffering from hypothyroidism often complain of “brain fog” or cloudy thinking, sometimes the treatment (synthroid) exacerbates preexisting “brain fog.”  Whenever ingesting any exogenous synthetic hormone, it is necessary to understand that it affects your entire neurophysiology, including your neurochemistry.  As a result, it isn’t surprising to learn that some individuals experience brain fog while taking synthroid.

If you experience a worsening of brain fog from synthroid, you’ll want to work with your doctor to adjust the dosage, consider alternative medications, and/or adjunctive treatments.  Most individuals that experience brain fog from synthroid, notice it most significantly at the start of treatment; this may be caused by too high/low of a dose.  Too high of a dose and you run the risk of sporadic, fast-paced, unfocused anxious thinking.

Too low of a dose and your preexisting brain fog from hypothyroidism remains.  Assuming you’re taking a properly-adjusted dose of synthroid, symptoms of brain fog will likely improve.  That said, it may take a couple of weeks for severe brain fog to subside after starting treatment.  In the event that it doesn’t improve, prescription of an adjunct pharmaceutical may be warranted to enhance clarity of thought.

Chest pain: In rare cases, synthroid users may experience chest pain as a side effect.  Due to the fact that chest pain could be a sign of a serious medical condition such as a heart attack, any synthroid user experiencing chest pain should seek immediate (emergency) medical attention.  Assuming medical conditions are ruled out as the cause of your chest pain, and it isn’t considered a serious adverse effect by medical professionals, it may be a side effect that you’ll have to deal with throughout treatment.

It is possible that the chest pain is a result of your body adjusting to synthroid, and that with time, the chest pain may subside.  In other cases, chest pain could be a sign that a user’s synthroid dosage is too high, leading to symptoms of hyperthyroidism, heart rate irregularities, palpitations, anxiety, etc.  It may also be necessary to consider that a subset of synthroid users may experience anxiety/nervousness, triggering overactivation of the sympathetic nervous system, and leading to pain in the chest area.

Cognitive deficits: Most individuals with legitimately diagnosed hypothyroidism experience a significant boost in cognitive performance when taking synthroid.  Suboptimal levels of T4 are known to impair cognitive processes and lead to deficits in executive function.  However, counterintuitively, a subset of synthroid users may notice that their cognitive performance significantly declines while taking the medication.

Deficits in cognitive function may be caused by too high of a synthroid dosage, leading to anxiety and inability to focus.  If you struggle with attention, critical thinking, planning, and problem solving after taking synthroid – there’s a good chance it’s from the medication.  To confirm that cognitive dysfunction is being caused by synthroid, it may be useful to employ cognitive assessments prior to treatment and reassess cognition during treatment.

If the results significantly differ between pre-synthroid and during treatment, you can confirm that synthroid detrimentally affected your cognition.  Cognitive dysfunction may be a serious concern for those in cognitively demanding occupations or academic settings.  If cognitive deficits are considered a severe side effect, a change of medication and/or adjuvant cognitive enhancer may be warranted.

Constipation: While many synthroid users report loose stools and/or diarrhea, others experience a lack of bowel movements and/or constipation.  If synthroid is making you constipated, and the constipation is severe/persistent, this side effect should be discussed with your doctor.  It is possible that strategic dietary adjustments and/or laxatives may prove helpful as to attenuate the synthroid-induced constipation.

In many cases, constipation caused by synthroid goes hand-in-hand with the aforementioned side effect of bloating.  For a bulk of synthroid users, constipation and bloating are unlikely severe enough as to cause functional impairment.  Furthermore, after several weeks of synthroid treatment, some users may find that constipation subsides.

Depression: A hallmark symptom of hypothyroidism is that of depression and/or low mood.  Typically, when hypothyroidism is properly treated with an agent such as synthroid, depressive symptoms completely subside.  However, some individuals using synthroid to treat hypothyroidism experience an increase in overall moodiness and feel extremely depressed directly as a side effect of the medication.

If you experience depression after taking synthroid, it is necessary to consider that it may be a result of suboptimal dosing (e.g. too much/too little).  A high dose may induce an anxious-depression, whereas a low dose may fail to treat the underlying hypothyroidism.  You may also want to consider that your particular neurochemistry may respond poorly to synthroid as a medicinal intervention, which in turn causes depressive thoughts.

Depression is a serious medical condition in and of itself, and should be interpreted as a sign that something is either amiss with synthroid dosing and/or that alternative options should be pursued.  Anecdotal reports indicate that depression may become so severe (as a result of synthroid), that it may prompt suicidal thoughts and feelings of hopelessness.  Talk to your doctor immediately if synthroid is making you feel depressed.

Diarrhea:  Synthroid may provoke increased frequency of bowel movements and/or looseness of stools.  Synthroid can cause gastrointestinal irritation in many users, leading to stomach aches followed by diarrhea.  It is diarrhea that may contribute to a small amount of weight loss among those who report losing weight while taking synthroid.

Should you experience diarrhea as a side effect, it should be discussed with your doctor – especially if severe.  Keep in mind that adjuvant administration of an over-the-counter agent such as Imodium may prove helpful in normalizing your bowel movements and minimizing gastrointestinal distress.  Also understand that diarrhea may be transient and subside with continued synthroid usage.

Dizziness: When first beginning synthroid treatment, some users report dizziness.  Although this isn’t a side effect that’s commonly mentioned to patients, it can occur in a subset of synthroid users.  Some individuals experience mild forms of dizziness, while others find that dizziness is so extreme – that they can barely maintain balance to stand upright and/or walk.

For most users, the dizziness subsides and/or improves within a week or two of treatment.  Some speculate that improper dosage of synthroid and/or abnormal TSH levels may be the cause of dizziness.  Upon adjustment of synthroid dosing and with continued treatment, most individuals notice a significant reduction and/or complete cessation of dizziness.

Dry skin: A side effect associated with synthroid is dry skin, which may be accompanied by itchiness.  Many users notice that their skin becomes drier, flakier, and more sensitive as a result of synthroid treatment.  It should be noted that dry skin is often a common symptom of hypothyroidism, the condition being treated with synthroid – making it difficult for patients to determine whether their skin is dry because of the medication or hypothyroidism.

To ensure that the dry skin is being caused by the medication, it is imperative that your TSH levels are checked and medically considered to be within an optimal range.  If your TSH levels aren’t within an optimal range, it may not be the synthroid that is causing dry skin.  However, if you never had dry skin prior to using synthroid and your TSH levels are within a normative range – the dry skin could be a side effect of your medication.

Eye problems: A multitude of synthroid users report side effects of eye dryness, itchiness, and blurred vision.  Some people feel as if there is no fluid and/or moisture surrounding their eyes and as if they cannot stop scratching their eyes due to the itchiness.  If your eyes dry out after taking synthroid, the constant scratching or brushing of the eyes to deal with itchiness may cause temporary bouts of blurred vision.

It is also understood that lack of moisture from the tear glands and tear ducts can cause inflammation, which could lead to blurred vision and/or eye problems.  It may be necessary to consult your doctor, as well as an ophthalmologist (or optometrist) for further information.  Switching medications may reduce eye dryness and/or visual changes, but you may need to safely utilize an exogenous moisturizer if your eyes continuously dry out from the synthroid.

Fatigue: Within the initial few weeks of taking synthroid for hypothyroidism, many patients report substantial increases in vigor and energy.  However, other patients report no improvement in energy level, or even worse, an exacerbation of fatigue and lethargy.  Testimonials from synthroid users have gone as far as to suggest that the fatigue induced via synthroid is so severe, that they cannot perform normal work and/or school-related tasks.

The fatigue experienced while taking synthroid may be accompanied by brain fog, inability to think clearly, and/or cognitive deficits.  If you feel as if synthroid has sapped every last ounce of physical and mental energy, and as if you can barely roll out of bed in the morning – it is important to understand that fatigue is a side effect.  In some cases, the fatigue and/or lethargy may be transient and only occur during early stages of treatment when dosing isn’t fully calibrated.

However, if the fatigue persists for months after taking synthroid – it is a smart option to discuss alternative treatments with your doctor.  Additionally, it may be necessary to consider various supplements and/or stimulatory agents (e.g. modafinil) to attenuate the synthroid-induced fatigue.  If synthroid has transformed you into a lethargic zombie, know that you’re not alone.

Fever: Individuals that take too much synthroid may experience a low-grade or moderate fever.  In cases of synthroid overdoses, fevers may be extremely high and resulting from hyperthyroidism or too much thyroid hormone.  If you’ve been prescribed too high of a synthroid dosage and/or the amount you’re taking is too high for your physiology to handle – your body may respond with a fever.

Since synthroid is a synthetically engineered form of T4, it is necessary to consider that for some users, increased bodily temperature may also be a result of inability to tolerate a non-bioidentical (synthetic) hormone.  It should be noted that fevers are often accompanied by chills and possibly sweats.  Should you experience an incessant fever that fails to subside after weeks of synthroid treatment – it may be a sign that your body is unable to tolerate it.

Fingernails cracking: A common, yet underreported side effect associated with synthroid is splitting, cracking, and/or brittleness of fingernails.  You may notice that after taking synthroid for awhile, your fingernails are suddenly cracking, weak, and/or brittle.  This could be especially uncomfortable, embarrassing, and/or problematic if your fingernails literally end up falling out.

To ensure that your fingernails stay healthy while taking synthroid, you may need to carefully monitor your nutritional intake as well as consider various adjunct dietary supplements.  Certain supplements may bolster the strength of your fingernails and offset the fingernail cracking as induced by synthroid.  For most synthroid users, fingernail cracking isn’t a distressing side effect, but one that is important to highlight nonetheless.

Hair loss: Among the most common side effects associated with synthroid is hair loss.  Do not be surprised if during the first few months of treatment, you experience hair thinning and/or significant hair loss.  Clumps of hair may fall out in the shower and you may feel as if you’re going bald directly as a result of synthroid.

A loss of hair can take a toll on self-esteem, lead synthroid users to feel embarrassed about their appearance, and ultimately cause depression.  Fortunately, hair loss is considered a transient side effect and should eventually subside by the fourth or fifth month of treatment.  In some cases, it can take awhile for your body to fully adjust to synthroid and for the hair loss to subside.

Some synthroid users cannot handle losing their hair and resort to alternative medications.  If you are worried about losing your hair and/or are experiencing substantial hair loss from synthroid, you may want to pursue an alternative treatment.  Keep in mind that if you can tough out the first few months of treatment – hair loss is unlikely to worsen.

Headaches: Many synthroid users experience frequent headaches as a result of treatment.  Fortunately for most, headaches are relatively mild and intermittent – rather than severe and chronic.  Headaches are most commonly reported among new synthroid users or those who haven’t fully adjusted to the physiological effects induced by the medication.

In some cases, adjustment to synthroid takes several months, and after this adjustment phase, headaches significantly subside and/or completely cease.  To cope with headaches caused by synthroid, you may want to consider taking an over-the-counter medicine for headache relief (as recommended by your doctor).  Some synthroid users have had to accept that headaches are a side effect of a necessary medication.

Heart palpitations: You may experience sensations that your heart is fluttering, skipping a beat, and/or beating loudly while taking synthroid.  Some users, especially those receiving too high of a synthroid dosage, may experience heart palpitations.  The problem with these palpitations is that they can cause anxiety over heart health, which in turn increases overall stimulation, and ultimately future incidences of palpitations.

To put your mind at ease, it is always best to make sure that you’ve ruled out serious heart problems that may contribute to a heart attack.  Additionally, working with your doctor to pinpoint an optimal synthroid dosage may be critical for a reduction of palpitations.  That said, managing stress, getting proper sleep, and utilizing adjunctive anxiolytics – may also help.

Heat sensitivity: Users of synthroid commonly notice that their body has become much more sensitive to warm and/or hot temperatures.  In fact, some users have stated that while taking synthroid, they simply cannot tolerate any heat.  If you find it difficult to step into a warm room and/or go outside on a sunny, hot, summer day – it may be that synthroid has caused you to feel extra sensitive to heat.

Some users may find that after several months of synthroid treatment, sensitivity to heat decreases and/or normalizes.  That said, this may be a side effect that you need to “put up with” if you’re attaining therapeutic benefit from synthroid.

Hot flashes: Anytime you’re tinkering with hormone levels, you run the risk of experiencing hot flashes or a sudden feeling of feverish heat.  Hot flashes may be accompanied by flushing of the face, sweating, and/or chills among synthroid users.  It is common to experience hot flashes if synthroid dosage is too high/low.

Furthermore, it is necessary to consider that hot flashes may occur due to the fact that your body hasn’t fully adjusted to the drug.  Also consider that if you experience recurrent hot flashes for a span of months after taking synthroid, it could be a sign that your body is unable to tolerate an exogenously-administered, synthetic hormone.  As you work with your practitioner to pinpoint the optimal synthroid dosage and continue taking the medication, hot flashes may subside.

Insomnia: A side effect that plagues many synthroid users is insomnia.  If after taking synthroid you find yourself unable to sleep at night, you are not alone.  Many individuals report (especially when first starting treatment) that they feel overstimulated, have racing thoughts, and feel heightened anxiety – all of which may interfere with their ability to transition from wakefulness to sleep.

Others may find that they wake up during the middle of the night, but are unable to fall back asleep after this waking.  Due to the fact that insomnia may have deleterious implications for neural health, it may be necessary to pursue treatment.  Sometimes insomnia is caused by too high of a synthroid dose, but other times it’s simply a normal side effect that eventually diminishes and/or subsides with time.

If you’re experiencing insomnia, you may derive benefit from sedative/hypnotic supplements and/or Z-drugs (pharmaceutical sleeping pills).  Discuss all potential interventions with a doctor and consider consulting a sleep specialist.  Minimizing your stress response via activities such as deep breathing and/or meditation may reduce the severity of insomnia as a side effect.

Irregular heartbeat: Synthroid may cause arrhythmia or irregular heartbeat in some users.  This may be different from palpitations which is essentially a fluttering sensation and/or perception that your heart is beating abnormally loudly.  If you’re experiencing an irregular heartbeat after taking this medication, you should consult a medical doctor to rule out potential drug-induced cardiac emergencies.

Most people notice a racing heartbeat and/or as if their resting heart rate is considerably faster than usual.  This is likely due to the fact that synthroid can be stimulating to a user’s physiology, especially when ingested at a high dose.  Heart arrhythmias should be regularly monitored, synthroid dosing should be reviewed, and adjuvant strategies to normalize heart rate may warrant consideration.

Irritability: Do you feel as if synthroid has transformed you from a happy-go-lucky, relaxed person into a raging, irritable maniac?  The contrast may not be quite that extreme, but many users report that after taking synthroid, they their demeanor changed from being relatively easygoing and relaxed – to one of sheer irritability and anger.  Irritability is often a sign that the neurophysiological changes as induced by synthroid may be unfavorable.

Synthroid may be altering neural activation and/or neurotransmission throughout your brain, which in turn could cause you to feel more irritable than usual.  Understand that synthroid dosing adjustment and/or continued treatment may reduce feelings of irritability.  However, if you know that you need to take synthroid, but the irritability is difficult to tolerate, discuss a potential concomitant psychiatric agent (e.g. an anxiolytic) to offset this side effect.

Joint pain: Some people claim to experience significant joint pain after taking synthroid.  The joint pain induced by synthroid may be insidious in that it gradually worsens over an extended duration of time.  You may not feel very much pain when you first begin synthroid treatment, but after several months and/or years of usage – you may suddenly notice an extreme pain in your joints.

Assuming you want to continue taking synthroid, you could explore natural options to cope with this joint pain such as collagen, glucosamine/chondroitin, anti-inflammatory agents, etc.  It may be tough to pinpoint whether synthroid or simply aging has caused your joint pain.  An easy way to test this is to go off of synthroid or try another medication and reassess the pain.

If you never had joint problems prior to taking synthroid, and suddenly noticed muscle weakness, swelling, and pain – there’s a good chance that it’s the medication.  This isn’t a commonly discussed side effect, but one that numerous users have reported.  If your joint pain continues to worsen, interferes with your ability to exercise and/or well-being – you may need to evaluate other treatment options.

Memory loss: In some cases, treatment with synthroid may result in transient memory loss.  Not only may you lose your ability to perform cognitively demanding tasks, but you may find it tougher to consolidate and retrieve short-term and long-term memories.  If after taking synthroid you feel extremely forgetful, but never had major memory issues prior to treatment, there’s a good chance that it’s affecting your memory.

Among individuals that report memory loss as a side effect, it is difficult to pinpoint whether the memory loss was triggered by the synthroid or a result of dysfunctional thyroid.  If you’re experiencing memory problems, it may be necessary to have your doctor reassess your TSH levels and synthroid dosage.  That said, a small percentage of synthroid users truly believe that the drug has permanently damaged and/or modified their ability to recall memories.

Menstrual changes: Many women taking synthroid notice changes in their menstrual cycle throughout treatment.  It is understood that hypothyroidism often has a propensity to cause heavy cycles or large amounts of menstrual bleeding.  Upon treatment with synthroid, women may notice that their cycles become lighter and there’s less overall bleeding.

Since the thyroid and ovaries are interconnected with the endocrine system, it makes sense that altering thyroid hormone has menstrual implications.  Women may also notice that it takes days (or in some cases) weeks longer to have their period.  This is an underreported side effect, but one that female synthroid users are likely to notice.

Mood swings: You may be increasingly prone to mood swings as a result of synthroid usage.  It is understood that synthroid can induce mood swings, thereby prompting negative emotions in an unpredictable manner.  Many users have reported an onslaught of negative emotional states associated with synthroid including: anger, anxiety, depression, irritability, etc.

In some cases, mood swings may subside as the body continues to adapt to synthroid.  In other cases, you may feel as if synthroid has caused a psychiatric mood disorder.  Assuming you absolutely need synthroid to treat hypothyroidism (no other options work), but are experiencing disconcerting mood swings, you may need to consider an adjuvant psychiatric medication to manage these negative emotions.

Some evidence suggests that synthroid treatment is capable of altering monoaminergic signaling and/or levels throughout the brain.  In particular, synthroid may decrease neurotransmitter precursors such as tyrosine.  Users often exhibit low dopamine, which may play play a significant role in influencing the synthroid-induced mood swings. (Source: http://www.ncbi.nlm.nih.gov/pubmed/9849813)

Muscle aches: A side effect that is popularly noted by synthroid users is muscle aches and/or pains.  Assuming you never experienced muscle aches prior to taking the synthroid, there’s a good chance that these are drug-induced.  Realize that the muscle aches caused by synthroid are usually mild, but may be annoying nonetheless.

Achy muscles may interfere with your ability to exercise regularly, which in turn may further compromise your overall health – and especially the health of your muscles.  Synthroid is a synthetic hormone that isn’t always well-tolerated by the body.  Muscle aches may be one of many possible reactions generated by the body as a signal that the exogenous substance is difficult to tolerate.

Nausea: A side effect that many synthroid users find difficult to cope with is nausea.  When first starting synthroid treatment, you may find yourself feeling nauseous every single day.  Although this nausea may not occur for an entire 24-hour period, it may interfere with your well-being, occupational and/or school work, and ability to consume food.

In rare cases, the nausea may be severe enough as to provoke vomiting.  For most synthroid users, nausea subsides after a week or two of treatment.  If you’re several months into treatment, but are still experiencing severe nausea as a side effect, it is necessary to discuss with a medical professional.

Nervousness: Although you may not feel significant anxiety and/or experience panic attacks while taking synthroid, you may feel a bit more nervous than usual.  The nervousness may interfere with your emotional well-being and/or overall functionality.  Feeling nerved up is especially common during the first few weeks of taking synthroid and may diminish in successive weeks.  If nervousness becomes severe, you may want to discuss anxiolytic adjunct interventions and/or ask your doctor to reassess synthroid dosing (and TSH levels).

Sleep problems: It is no secret that synthroid can affect your ability to get a good night’s sleep.  In addition to causing insomnia (inability to fall asleep), synthroid may interfere with your ability to get deep, restorative sleep.  It may also cause broken sleep with frequent episodes of waking up throughout the night.

A subset of users report that after taking synthroid they don’t get enough quality sleep, while others report sleeping too much (oversleeping).  If synthroid is causing sleep disturbances, it is necessary to do whatever you can to correct these disturbances as soon as possible.  Disturbed sleep can impair cognition, cause excessive daytime fatigue, and may lead to other deleterious health complications.

While sleep may normalize after weeks (or months) of synthroid treatment, a hypnotic may be prescribed to ensure that sleep disturbances aren’t taking an additional toll on your health.  You may also want to make lifestyle changes to ensure a healthy circadian rhythm.

Stomach aches: Synthroid can cause an upset stomach, stomach cramps, and/or mild stomach pains in certain users.  If you’re experiencing stomach aches while taking synthroid, it may be that the medication is irritating your gastrointestinal tract.  This may also be especially noticeable since synthroid is recommended to be taken on an empty stomach (at least 30 minutes prior to eating); this enhances its absorption.

Unfortunately, taking any medication on an empty stomach often increases propensity to experience stomach aches.  Some individuals find that stomach aches diminish with continued, regular synthroid administration.  Others may need to come to terms with the fact that mild stomach aches may always occur while using synthroid.

Suicidal thoughts: There are reports of synthroid users feeling so depressed from taking the medication, that they’ve contemplated suicide.  Individuals with underlying neuropsychiatric disorders (e.g. major depression, anxiety disorders, PTSD, etc.) may be particularly sensitive to the neurophysiological changes induced by synthroid.  That said, even those without preexisting psychiatric disorders may be prone to negative thinking, mood changes, and possibly suicidal thoughts as a result of synthroid.

Changes in levels of T4 alters a user’s entire neurophysiology including: gene expression, neural activation, neurotransmission, brain waves, arousal, etc.  Studies have shown that synthroid administration particularly reduces concentrations of dopamine in various parts of the brain.  The culmination of these changes may cause some individuals to feel suicidal.

In some cases, suicidal thoughts may be transient and subside as synthroid is continued and/or dosing adjustments are made.  If you feel suicidal after taking synthroid, it is necessary to seek immediate medical attention.  Your doctor may be able to switch your medication, adjust your dosage, and/or prescribe an adjunct agent to mitigate depressive thoughts.

Sweating: Many synthroid users report profuse round-the-clock (24/7) sweating when starting treatment.  In some cases, the sweating will subside and/or lessen with time.  In other cases, the sweating is continuous and considered an unavoidable side effect of synthetic hormone treatment.

Know that synthroid could cause you to sweat excessively throughout the day, leaving your school/work clothing soaked by the afternoon.  While not everyone will experience and/or notice daytime sweating, others may notice that their bed sheets are drenched in sweat upon waking.  Synthroid elicits a profound effect on the endocrine system, which can affect thermoregulation and ultimately lead to increased sweating.

Swelling: You may notice that your fingers, toes, limbs, or other body parts swell up after taking synthroid.  The swelling may be mild at first, but progressively worsen throughout treatment.  If you wake up one morning and your fingertips appear significantly larger than they did before you began treatment, just know that this is a reported side effect.

Most individuals won’t swell to gigantic proportions, but it may be obvious that some swelling has occurred.  For certain users, swelling may be most noticeable when first beginning treatment and thereafter, it may completely subside.  That said, the swelling may be significant enough to cause joint and/or muscle pain – especially if it worsens over time.

Tiredness: As was already mentioned, synthroid can cause fatigue or feelings of lethargy.  However, some people may not only feel fatigued after taking synthroid, but extremely drowsy, tired, and/or sleepy.  Since hypothyroidism is associated with feeling excessively tired throughout the day, synthroid users should monitor their TSH levels and ensure that they are receiving an adequate dose of the drug.

Assuming your dosage is properly calibrated, yet you’re still feeling sleepy – it is possible that the tiredness/sleepiness is caused by neurochemical changes and/or interference with sleep.  You may want to consult a sleep specialist to determine whether the drug is affecting your ability to get deep sleep at night; lack of deep, restorative, delta sleep could be the culprit for your daytime tiredness.

If you are still feeling extremely tired, and the onset of tiredness occurred after you started synthroid, it may be necessary to consider that your body doesn’t respond well to a synthetic chemical or this particular drug.  You may want to discuss alternative options with your doctor.  If no alternatives exist, your doctor may consider prescribing a eugeroic or wakefulness-promoting agent so that you don’t drift off to sleep throughout the day.

Tremors: Some individuals notice that while using synthroid, they experience tremors or shakiness.  Among those that experience tremors from synthroid, most are considered mild and do not cause significant functional impairment – they are relatively benign.  They may occur most frequently in the hands and/or feet.

If you are experiencing tremors from synthroid, these should be discussed with your doctor.  It is possible that your dosage may need adjusting and/or that a different medication may reduce the occurrence of tremors.  Additionally, prescription of an adjuvant medication may decrease tremors or shakiness.

Weight changes: Most synthroid users experience some degree of weight change; sometimes significant and other times modest.  Changes in weight are most common during the first several months of treatment, and as the body acclimates itself to the synthroid, weight changes often subside.  However, many users report chronic, ongoing weight changes that persist throughout their entire term of treatment with synthroid.

Synthroid is known to affect appetite, metabolism, gastrointestinal function, and possibly gut bacteria – in certain users.  If synthroid is reducing your appetite, is ramping up your metabolism, and causing diarrhea – you’re likely going to lose some weight.  If synthroid is making you insatiably hungry, causing food cravings, decreasing your energy, and interfering with your ability to exercise – it may cause some weight gain. (Read: Synthroid and Weight Gain).

Although some weight loss is thought to be more common than weight gain among synthroid users – both have been reported.  It is therefore important to avoid overgeneralizing that everyone taking this medication will experience exactly what you’ve experienced in terms of weight change; some users may fluctuate in the opposite direction. (Read: Synthroid & Weight Loss).

Note: Understand that most users will not experience every single aforementioned synthroid side effect.  If you have a question about a particular side effect that you’re experiencing while taking synthroid, consult a medical professional.  Also realize that certain adverse reactions (e.g. chest pains and/or rapid heartbeat) may be caused by too much synthroid; consult your doctor if you have any signs of hyperthyroidism.

Variables that influence Synthroid side effects

If you’re taking synthroid, it is necessary to consider variables that influence the severity and number of side effects that you’re likely to experience.  Influential variables include things like: synthroid dosage, co-administered drugs, term of administration, and time of dosing.  Although the dosage may be the most influential variable, all variables should be contemplated if you’re experiencing side effects from synthroid.

  1. Synthroid Dosage (Sensitivity)

The dosage of synthroid taken on a daily basis can have a profound effect on whether you’re likely to experience unwanted side effects.  Dosing with synthroid needs to be as precise as possible to avoid side effects and severe adverse reactions.  Individuals prescribed synthroid at suboptimally high levels are the most likely to experience noticeable, unwanted side effects.

There are many problems associated with too much synthroid.  Since synthroid is an exogenous form of thyroxine (T4) hormone, ingesting too much synthroid could lead to side effects resembling hyperthyroidism.  Furthermore, synthroid is also “synthetic” and not bioidentical, which in turn could increase propensity of adverse reactions solely based on the lack of biological compatibility, especially at high doses.

Low-dose synthroid users are less likely to experience side effects from the medication and more likely to still experience symptoms of hypothyroidism (or another condition being treated with synthroid).  At lower doses, it is easier for the body to accommodate the non-bioidentical, synthetic material and tolerate some hormonal stimulation.  That said, when a certain threshold of hormonal stimulation is surpassed with high-dose synthroid – side effects are virtually guaranteed.

Note: Medical professionals should be aware of the fact that synthroid and levothyroxine-based medications are narrow therapeutic index (NTI) agents.  If the dosing is improperly calibrated even slightly, you may experience adverse effects.  Be sure to work with a doctor that prescribes the minimal necessary amount for an optimal TSH level.

  • Source: https://www.synthroid.com/medication/check-your-pill
  1. Co-administered substances

If you’re solely taking synthroid (and no other medications or supplements), you won’t need to consider this variable as influencing your side effects.  However, if you’re taking synthroid and a cornucopia of pharmacological and/or supplemental agents – it is necessary to consider that there may be interactions.  Something as simple as taking a multivitamin along with synthroid is known to decrease its effect, which could lead to suboptimal therapeutic outcomes and/or an increased incidence side effects.

Prior to taking another drug and/or supplement with synthroid, discuss potential contraindications with a medical professional.  If you’ve been taking synthroid along with another medication and/or supplement, but weren’t specifically instructed to do so by your doctor, it could be that the simultaneously administered combination triggered side effects.  You may also want to consider whether the co-administered substances have synergistic and/or antagonistic neurophysiological effects.

For example, someone taking synthroid along with a psychostimulant (e.g. Adderall) may find that the combination synergistically provokes anxiety, heart palpitations, and side effects associated with overstimulation; this may be especially noticeable if synthroid dosage is too high.  On the other hand, some drugs and/or supplements may be helpful when taken on the same day as synthroid.  For example, individuals experiencing hypertension may benefit from taking a beta blocker along with synthroid to reduce blood pressure.

Always realize that co-ingested substances can either cause contraindications (interactions), as well as potentiate or mitigate various neurophysiological responses to synthroid.  Be sure to review the dosages of the co-administered substances as well as times of administration with a medical doctor to minimize likelihood of interaction-based side effects.

  1. Term of administration

The cumulative term of synthroid administration may also affect the side effects that you’re likely to experience during treatment.  Some side effects that you experience during a short-term (e.g. first few weeks of treatment) may subside over a moderate and/or longer-term of treatment.  On the other hand, some side effects that may have been nonexistent over a short-term, may only emerge after an extended, long-term of synthroid treatment.

Short-term: Nearly everyone experiences some side effects when they first start taking synthroid (and many other medications).  Side effects are often most prominent during the first few weeks of treatment.  For example, you may notice hair thinning and/or loss, mood changes, and nervousness over the short-term.

However, many of these short-term effects diminish and/or subside with continued treatment.  A reason many short-term side effects subside is because a user’s neurophysiology has adapted to the synthroid.  Additionally, the doctor will have had adequate time to pinpoint a precise synthroid dosage for optimal TSH levels.

Moderate term: After several months of treatment, many short-term side effects begin to diminish.  You may notice less hair loss (or that your hair is no longer thinning), your mood and energy has improved, etc.  At this point the doctor is likely to have precisely calibrated your synthroid dose and your neurophysiology may have adjusted to the medication.

You may still experience some unwanted side effects, but many short-term side effects will have improved.  However, you may also notice the onset of some new side effects that didn’t occur during the short-term.  The emergence of new side effects should be carefully monitored, as they may progressively worsen with continued treatment.

Long-term: Over an extremely long-term (e.g. years) of treatment, many synthroid users find that short-term side effects have completely subsided and that they can tolerate the medication well.  However, some side effects that they had never experienced over short/moderate terms may emerge.  At this point, it may be difficult to confirm with 100% certainty that the synthroid is the cause of the side effects.

Many people find it difficult to distinguish long-term side effects of synthroid from normal aging.  You may notice the onset of achy joints, swelling, memory problems, cognitive deficits, and/or weight changes.  Since the long-term effects of synthroid aren’t well documented in scientific literature, most medical professionals assume that these problems are a result of lifestyle issues rather than from the medication; and in some cases it may be a combination of both.

  1. Dosing specifics

Medical documentation indicates that synthroid is to be administered as a single dose, once daily.  This dose is suggested to be administered in the morning, at least 30-60 minutes prior to eating breakfast.  Additionally, synthroid is recommended to be taken at least 4 hours prior to any other drugs or supplements, especially those that are known to interfere with its absorption.

If you’ve been taking synthroid along with food and/or later in the day than is medically recommended, it may decrease the likelihood that you’ll attain therapeutic benefit.  Time of synthroid dosing is of critical importance not only to ensure that synthroid is properly absorbed, but to minimize likelihood of side effects and/or interactions.  To decrease propensity of side effects related to dosage timing, synthroid is recommended to be taken at the exact same time each day.

Synthroid (Levothyroxine): Do the benefits outweigh the side effects?

If you’ve been taking synthroid, it is necessary to track whether the therapeutic benefits attained from the medication outweigh side effects and adverse reactions.  A subset of synthroid users may be unable to tolerate the medication as a result of severe adverse effects experienced while taking the drug.  For these individuals, it will be obvious that their neurophysiology cannot handle the synthroid and a change of thyroid medication will be necessary.

On the other hand, another subset of synthroid users may experience no significant side effects.  They may find that synthroid successfully keeps their TSH level within a healthy range and significantly improves their physical and mental energy.  For those that derive nothing but benefit from synthroid without any significant side effects – continued usage is a “no brainer.”

Most synthroid users will fall in between the extremes of “intolerability” and “optimal tolerability.”  You may find that synthroid treats your hypothyroidism, but also causes dry skin, moodiness, and modest weight changes.  Assuming that the medication is effectively treating your medical condition with just a few unwanted side effects, it is usually worth continuing.

However, if after taking synthroid you’re getting some therapeutic benefit, but you also experience: severe brain fog, fatigue, depression, and anxiety from the medication – discontinuation and/or an alternative medication may be warranted.  Overall functionality should be improved as a result of taking synthroid – not further impaired.  Remember that while your doctor prescribed this medication because he/she believes the benefits are likely to outweigh the side effects – not everyone responds favorably to this treatment.

It is ultimately a personal decision as to whether you’d like to continue taking synthroid, switch to another medication, and/or alternative intervention.  You may find it helpful to keep a journal of your entire synthroid treatment to determine how you feel over a long-term span, rather than being prisoner to short-term, transient, or moment-by-moment side effects.  If you feel as if synthroid isn’t a good fit for your neurophysiology, discuss this with your doctor.

Possible ways to reduce Synthroid (Levothyroxine) side effects

If you’re taking synthroid and experiencing unwanted side effects, below are some side effect mitigation strategies that you may wish to implement.  Prior to implementing any of these strategies, consult a medical professional to verify efficacy and safety.  Examples of some strategies for reducing unwanted synthroid side effects include: dosage recalibration, review dosing instructions, continue using, and/or revision of adjunct agents.

  1. Dosage recalibration

If the dosage of synthroid that you’re taking is too low, you run the risk of experiencing symptoms of hypothyroidism (or the condition being treated with synthroid).  On the other hand, if the dosage of synthroid is too high, side effects may be extremely likely.  The goal of your doctor should be to determine the minimal effective dose of synthroid to normalize your TSH levels.

Synthroid is a medication with a NTI (narrow therapeutic index), and as such, if the dosage is slightly “off” – unnecessary side effects may ensue.  Have your doctor reassess your synthroid dosage and reevaluate your TSH plus other thyroid parameters.  If your doctor determines that your dosage was too high, a reduction may mitigate various synthroid side effects.

  1. Review dosing instructions

Instructions for dosing with synthroid should be reviewed prior to initial administration.  Many people taking synthroid listen to their doctor’s dosing instructions, as well as those given by a pharmacist, but fail to actually implement them.  Time of dosing as well as whether synthroid is taken without food – are important factors that affect therapeutic response rates and side effects.

Synthroid is recommended to be taken at least 30 to 60 minutes before breakfast in the morning.  If you’re experiencing side effects from taking synthroid 30 minutes before breakfast, you may need to increase the gap between synthroid ingestion and food consumption to 60 minutes.  Additionally, if you’ve been somewhat inconsistent in timing of administration – this could increase side effects.

Be sure that you’re taking synthroid on an empty stomach, as a standalone agent (without other medications unless instructed by your doctor), at a precise time each morning, and at least 30 to 60 minutes before consuming food.  Following these exact dosing instructions may prevent certain side effects from occurring and maximize likelihood of therapeutic efficacy.

  1. Continued usage

In many cases, side effects experienced when starting synthroid will diminish and/or subside after several weeks (or months) of treatment.  When any new exogenous medication is introduced to the body, it disrupts homeostatic processes and can trigger side effects.  However, with continued administration and dosage calibration, a user’s neurophysiology adapts to the presence of synthroid and side effects (e.g. hair loss) subside after several months.

If you’ve been using synthroid for under 3 months, side effects are common and to be expected.  However, if you’ve been using synthroid for considerably longer than 3 months (e.g. 1 year) and they are difficult to cope with, you may need to switch thyroid medications, consider adjunct medications to offset the side effects, and/or discontinue treatment.  Always discuss the severity of synthroid-related side effects with your doctor.

  1. Revise adjunctive agents

If you’re taking other drugs and/or supplements along with synthroid, it is understood that these could either: interact with synthroid, potentiate synthroid-related side effects, or offset synthroid side effects.  Discuss potential medication contraindications with your doctor, as well as side effects that could be caused by potentiation of synthroid-induced neurophysiological effects.  Assuming synthroid is being administered at an optimal dose, other agents aren’t administered for at least 4 hours after taking synthroid, and there aren’t any contraindications – interaction side effects are unlikely.

However, you will want to work with your doctor to determine whether certain medications and/or supplements could be beneficial to eliminate from your current regimen.  It may turn out that the side effects you thought were from synthroid, were actually from another co-administered substance.  That said, your doctor may also recommend adding another medication and/or supplement to your regimen to counteract synthroid-induced side effects (e.g. an antihypertensive agent to treat hypertension and/or nervousness); be open to these recommendations as they may help significantly with side effects.

Have you experienced Synthroid side effects?

If you’ve taken synthroid, share a comment mentioning whether you’ve experienced significant and/or noticeable unwanted side effects.  Document the particular side effects as well as their respective severities (on a scale of 1 to 10) and mention when you first noticed them during your treatment.  If you’re a short-term user, it is important to realize that many side effects will diminish and/or completely subside after several months of treatment.

However, if you are a longer-term user, leave a comment noting whether any side effects have lingered throughout your treatment and/or emerged over a long-term of administration.  To help others get a better understanding of your situation, share some details such as: the condition you’re treating with synthroid (e.g. hypothyroidism), your current dosage, other medications and/or supplements that you take, your time of synthroid dosing, etc.

For those that have experienced side effects from synthroid, share any strategies you’ve found beneficial for reducing them (e.g. using another medication).  Understand that if you’re experiencing severe side effects from synthroid, you may want to consider alternative pharmaceutical options, bioidentical hormones, and/or correcting the underlying causes of your underactive thyroid (e.g. stress, diet, environmental toxins, etc.).  Not everyone can tolerate synthroid and it should not be considered a utopian hormonal intervention; no medication is an optimal fit for every user.

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51 thoughts on “Synthroid (Levothyroxine) Side Effects & Adverse Reactions”

  1. I have been on Levothyroxine for 5 months, as well as Metformin. I still have occasional stabbing pains in my abdomen, along with gas, bloating, constipation, and worsened back pain. Sometimes I have brief dizzy spells, and nausea as well.

    Of course, I also have depression because my quality of life is so diminished. The only good thing to come out of all this is that I have lost 40lbs. Not sure the pain is worth it though. Body doesn’t look better anyway because of the bloat.

    I can’t wait to get off both meds, but so far my diabetes is not responding to the Metformin & I know my Dr. won’t allow me to quit either one. I sometimes get such horrible back pain that I can’t tell if it’s my back or my abdomen.

    All I know is it hurts. The only answer to the pain from my Dr. was, “take some Align probiotic.” I have been taking Ibuprofen & probiotics and am still in pain. Wish I could just feel normal again.

  2. I feel much better when totally OFF of synthroid. It makes my heart race so badly that I now have a heart monitor I wear. I am starting to take Kelp and getting off the synthroid.

    It also made my hair fall out after I started taking it and my hair was GREAT before I took it. To me, the side effects are not worth taking the medication. My heart palpitations were so scary I almost ended up in the ER.

  3. I’ve been taking levothyroxine (75mcg) for almost 2 weeks. I’ve been having horrible mood swings and I have yet to start my period, I am 8 days late. My period has ALWAYS been like clockwork. I still have all of the PMS symptoms, yet no period.

    I called my doctor’s office and they told me that a missed period is not really a side of effect of this medication and that I must be pregnant (took 2 tests, both negative). I am so grateful I came across this website, now that I know that a late period is a underreported side effect, at least I know it has happened to others. So frustrating!

  4. I’ve taken 0.05mg of Synthroid since birth. In the 28 years I have taken it I would say that the majority of issues that continue on a daily basis are dry skin, intolerance to hot/cold, increases chance of diarrhea, brittle nails and having generally less energy than those around me.

    I find I am constantly hungry and need o snack all the time or I grow irritable due to lack of food. In some portions of my life I have become very anxious, have tremors, hot/cold flashes, upset stomach, insomnia and trouble thinking clearly. I note these times where I feel very strange when I am in increased stress environments for a prolonged period of time (mostly due to work).

    I did not think much of it at the time. But thinking back on it now, it was probably because I am receiving to much of the drug and any long term stressor seems to bring up underlying issues with the medication. I am currently looking into lowering my dosage to see if it helps.

  5. I’m so glad I happened across this web page as I have been searching for some kind of explanation as to what I have been experiencing and I have not gotten anything from my doctors. I am three weeks into my Synthroid I started on 50mcg but was feeling awful, I was upped to 150mcg and felt worse, then doctor backed it up to 75mcg and I still felt horrible.

    The only OK days I have are the once where I skip my medication. The side effects have been debilitating to the point that I have not been to work in a week, I cant drive a car, I cant manage anything around the house.

    I have had extreme fatigue, very bad brain fog where I can’t think or concentrate on anything, pressure in my head, sweating, cramping, and more. This has given me some peace of mind at least that it’s my medication causing this and not some other horrible disease.

  6. I too have all the symptoms above. They took my thyroid out because I was having trouble swallowing, was on nexium for 9 years for Gerd. Found out it was very large. Took them that long. Put me on synthroid and said you’ll be fine. They don’t tell you nothing about it. They just think we are over reacting when we complain. Synthroid should not be on the market, our doctors should be taking it then things would happen. It’s a shame we are held hostage by some doctors.

  7. I started out on synthroid for 1 1/2 yrs, was having all night dreams which caused me to feel like I had not been to sleep when I woke up. I got up to go to work cause I had to but to get up and go fishing or hunting I found myself putting it off for a couple more hours so I could sleep more.

    I talked to the NP that started me on the meds about the issues and she said she had never heard of any of these symptoms and she didn’t have a miracle pill to fix it and couldn’t help me anymore and sent me to a specialist. I didn’t get any results from him either. So, I went back to my family doctors practice and told them I wanted to see the Dr and not the NP.

    My Dr switched me to the generic – had some issues for 6 months, lethargic, very irritable (quick tempered) and depressed. So, I quit taking meds for 2 weeks, all symptoms went away. I went back to my Dr and told him what was going on, and that I quit taking the meds. Bloodwork was taken and the results were bad, I started back on the generic meds. I have been on them now for 6 weeks and feel good…

    In between all this mess, I got online and read up on what foods, fluids, pills that affect the thyroid meds and found out a lot – I was taking my cholesterol meds with the thyroid meds (that’s a no no) – also not drinking enough water when taking meds, drinking coffee too soon after taking meds and eating too soon after taking meds as well. So I changed all that and it made a difference.

    I had also switched to taking at night before bed but that didn’t work for me – couldn’t go to sleep for a couple hours – but I did read in some forums that taking at night helped some folks though. I went back to taking in the morning at 5:00, then have coffee at 6 when I get to work, then have a little breakfast at 7. It’s now going good. I am glad that I did some research and read the forums, it sure helped out. I got some good info on People’s pharmacy website.

  8. I am on levothyroxine. I experience drenching night sweats and abdominal pain with diarrhea. Joint and muscle pains. Intermittent hives and bruises.
    My GP refuses to acknowledge that my symptoms are due to the drug. He keeps pointing out that the lab results are normal.

    • I have been hypothyroid for about 17 years now. I’m a 58 year old female. I hate to tell you all this but it is going to be an ongoing struggle to get the correct dosage. I am currently working with my Endocrinologist who thinks that I was taking too much Synthroid, 188 mg, and had backed me off to 175 and now 150.

      I am once again tired and depressed… sigh… Levothyroxine did not work for me either. I have had palpitations, fatigue, depression, constipation, intolerance to heat and a puffy face. I have also gained a ton of weight. The weight is not all the hypothyroidism, but lack of energy means not much exercise happens and when you don’t burn off calories you add weight.

      My blood work hardly ever seems to match up to how I’m actually feeling! In other words the blood work says I should be full of energy and be depression free. NOPE! I can guarantee my doctor will end up increasing the dosage again or trying me on Amour thyroid, made from desiccated pigs thyroid, because it’s supposed to be better than the synthetic meds.

      I don’t want to depress you more, but you HAVE to be your own advocate. Regardless of what the blood work says – if you still feel like crap your doctor needs to tweak the dosage or try something else.

      • “you HAVE to be your own advocate”

        YES! I’ve been locked in a struggle with a doctor, I have Thyroid issues, but also insomnia. I keep getting sent to sleep-psych specialists because I’m supposed to have “Negative associations about sleep & negative sleeping behaviors.”

        When I ask for descriptions of this it’s completely unlike anything I’m experiencing, they insist that bad thoughts are going through my head & don’t do “going to bed/sleep properly”. Today I laid it out where they’re wrong & that got right up their nose so I responded with “When did Evidence Based Medicine leave the room?”

        Result? My Doc dumped me. I’m now seeing another one later this week, someone I found myself & at least I have some chance of it working as they specialize in Endocrine/Sleep Disorder.

  9. Started levothyroxine .25 and started having headaches within two weeks of taking meds. I have dry skin, hot flashes, headaches that last for weeks, and migraine. Pain starts at back of head and works its way up and to the sides. Does anyone else experience this?

  10. OMG! I have been on medication for hypothyroidism for 15 years. Starting with 300mcg per day then after 4 years and until present day, 200mcg per day. I have been on synthroid for the last ten years. I suffer from almost all the issues discussed in this article.I have been to my GP many times over the years complaining of these issues and my doctor always tells me it cant be the medication.

    I’m sure it is though. The extreme temperature sensitivity is nasty, especially the heat flashes, and it’s not menopause as I am passed that. Headaches, inability to get restorative sleep, extreme fatigue (one doctor has diagnosed me as having chronic fatigue) severe skin sensitivity, hair loss (including large bald patches), severe eye dryness, stomach problems, heart palpitations, weight gain, bloating, chronic depression, anxiety, memory loss, and severe brain fog.

    If only I had known what this drug would do to me before I started taking it… My doctor tells me that I will have to take thyroxine forever. Bummer huh.

    • Omg, your post just explained my life and exactly what I am living through. I’ve been on armour for awhile and then synthetic. I hate both. I feel all of what you do, to a T. Have you improved? I am currently sleeping on beach towels because I sweat so much in the first hour, no matter what that I soak the sheets and comforter. It is crazy the state of dehydration I am in on top of everything else. I am a 44yr old female with Hashimotos, SLE, RA, any much more, blah.

  11. I have been taking Synthroid for a couple years now. I started out at 25 mcg, went up to 50 and now to 75 to get it at the correct level I’m told. It hasn’t been easy, and it still isn’t. My muscle issues (or Charley horses), have gotten better. I have gained weight, I was at 182 and now at 197, I eat the same food now as I did before I started the meds.

    I also have sweating at night during sleep time, I have constant dreams, I don’t feel like I slept at all some mornings, although it is better than it was. I have fatigue, irritability, mood swings, nervousness, depression at times and now this morning I woke up at 3 am, I don’t think I went back to sleep fully, the thoughts or maybe I was dreaming was the worst yet.

    It’s been a little over 2 years on this med, why is this happening now I don’t understand, maybe I haven’t adjusted completely to the 75 as that just happened mid year 2016. If the Dr can’t help and this doesn’t subside soon, I may be divorced.

  12. I have been on Tirosint, 50 mcg for awhile. I have all of these awful side effects. The chest tightness is awful! I have it all day. The endos say it’s not the medication. This is the only medication I take.

    I was completely healthy before this medication. These doctors are so naive about this medication. They have no clue about side effects. Didn’t they go to medical school??? This is the most dangerous drug. It screws up your natural hormones.

  13. I am so glad I found this. My doctor keeps saying, you can’t be allergic to thyroxine. Are you sure? I had a thyroidectomy in February of 2016. Ever since I have been so sick. I was initially put on NDT, felt absolutely awful.

    I was then put on T3 only. In many ways, I felt better, but not great. I could never get up to the dosage that is recommended. I also felt like it was hard on my adrenals.

    However, started on compounded T4 and within a matter of days, but entire body was freaking out. I could not stop sneezing, I developed a full on rash on my legs and all I did was itch. I started to go to all of these doctors for everything. An immunologist for the allergy, the sneezing, the never ending cold that I felt I had.

    I went to the dermatologist twice covered in eczema, something I have never had in my life. I am being told, “Well, they are hypo symptoms.” If I never had this prior to taking the medication, why am I having them now? WHY? I was on T3 with the T4 (compounded) and the more I went up on T4, the worse it got.

    When I was on 25 mcg of T3 and 50 mcg of T4, it became awful…this is 3 months in. I stopped sleeping. Went up to 60 mcg of T4-everything started going berserk. I had never had anything like it before. My lips started peeling. My eyes became so dry, I started going to the chiropractor twice a week because my neck and shoulder were in constant pain, I had daily migraines.

    I felt awful. Blood work was showing, that my numbers were looking better and yet, I am feeling like death. My rash that I developed was nuts. I decided to not take the medicine for 36 hours, I noticed my body calmed down. I took it. Within one hour, my neck went into spasm, I had chest pain, I had TMJ, a migraine came on… 3 hours later, I had full on itching all over my body.

    My scalp, everything. I was up all night. This is now about 7 nights with zero sleep. I started going crazy. With that, I made the decision out of desperation, lack of sleep and feeling like I can’t go on anymore…I am going to stop it. First night I have slept in weeks.

    Itching has stopped and my neck is not hurting. It’s been 48 hours since taking the medication. I see my doctor tomorrow to go over what my next option is. Many on here are hypo can just stop their medication and live with being hypo. I can’t. I have no thyroid. I would die without some form of medication.

    • It’s very difficult, isn’t it? So sorry you are having a sensitivity to the meds. I have been on it three months, Synthroid, and I think I have a sensitivity to it too. Hot flashes and very red face many times a day. How to get your doctors to help you change meds gently is what I am looking for. I hate taking this. I changed my diet, no soy, no gluten, no legumes, no fruit juice, and I am still trying to figure this all out. Ugh.

  14. I had a total thyroidectomy in August 2013 and have been taking Synthroid (non-generic) at several doses since with incredible chest pain unless the dose is as low as 88 which is not enough. I have been to the emergency room 3 times and had 3 total heart workups.. my heart is fine. I have had three endoscopies to rule out acid reflux, 1 24 hour acid test, 1 48 hour acid test, 2 manometry tests.. all negative.

    This pain is 100% a result of this drug! I want my life back. Tried NDT last year.. couldn’t do it.. still had chest pain that no one can figure out and they refuse to say it’s the synthroid but I know it is.

    I know this is not advised but.. the only way I can tolerate enough of this drug is to take 50 MCG at 3:00 am and 44 mcg at 11:00 AM, one hour before lunch, along with 5 mcg of Cytomel.. chest pain still exists but its tolerable this way.

  15. I take a compounded T3/T4. Synthroid only made me worse. I had blood tests for TSH, T3/T4, reverse T3/T4, and Free T3/T4. All of these numbers need to be in range and most doctors will not test for all of them unless you push them.

  16. After thyroidectomy this past May, I started with 137mcg. L-thyroxine. After 6 weeks it was reduced to 112 mcg, then after another 6 weeks it was reduced to 88 mcg. I’m due for another blood test next week. I am suffering with severe dry eye, leg cramps, palpitations, leg cramps, numbness in hands, feet and lips. After severe head trauma and treatment for an auto immune disorder years ago, my body has become intolerant to most medications, including vitamins and some OTC meds.

    My endocrinologist doesn’t think some of the symptoms are caused by the current med. I have also been on BP med for years. I am currently very tired and uncomfortable. A friend who is a retired nurse is on Synthroid, not the generic. She feels the “brand” is better. Any suggestions?

    • I also had thyroidectomy due to head neck injury. Before surgery my glands enlarged and wrapped around my vocal cords. I went from hypothyroidism to hyperthyroidism and was loosing 1-3 lbs daily before I found a specialist to operate. My glands were literally squeezing my throat shut.

      They removed 80% of the glands and scraped my vocal chords. It took two months to whisper and over a year to totally knit everything together. My surgeon told me he left a small portion of glands that should be enough but if I ever needed thyroid medicine only take Synthroid!

      Twenty years later the small piece wasn’t enough because my body had absorbed it. Forgetting my drs advice after many years my new doctor prescribed generic Levothyroxine. It didn’t work plus my vocal chords don’t get sufficient blood flow and I can’t talk. I have since argued with several doctors and hospitals that have made me bring my own medicine because they won’t carry it – only generic.

      Synthroid doesn’t contain filler and is T4 only. So this has happened at least thee times in the fifteen years. Hope you’re going to find what works best for you. Only you know how you feel and hormones are so sensitive! Good Luck.

  17. I have been on Levothyroxine for 8 years. The doses have gone up depending on the all the T tests. The only major complaint I have which is a killer for me is “SWEATING”!!. I might as well be living in a rain forest. I live with an air conditioner most of the year. Even when I’m out shoveling snow I come in soaking wet.

    There is also the hair loss, but my OBGYN said it’s the type that does grow back in. After looking at people’s comments for years, I’m now convinced there is nothing to stop the sweating. It’s sad when you have to carry around a fan or face cloth when you go out in public and have to explain why you look like a drooling St. Bernard. It seems to be one of those things you have to live with.

  18. YES! I have experienced a majority of the above symptoms. It felt extremely hypothyroid. I thought I wasn’t taking enough. Then my thighs, adductors, perilous, and shoulders started aching more and more until I couldn’t sleep at night. I switched to Naturethroid two months ago.

    My hair stopped falling out. I am thinking better. I am sleeping through most nights. And the muscle pain and weakness has greatly diminished. Natural desiccated thyroid works better for me and is much cheaper. I get it at Costco pharmacy.

  19. My wife has been taking synthroid for 8 years. My wife started to be depressed so the doctor gave her Zoloft. After that doctor gave her Buspirone because she had panic attacks. Shortly after that she started to lose her memory so they thought she had Azheimer’s. Her memory has gotten worse. I’m going to see if I can take her off of synthroid before she is completely gone. Thank you Mental health daily

  20. I had no idea that every side effect listed here I have suffered with in the 25 years I was on this drug. In the past few months I weaned myself off due to my thyroid feeling like a golf ball and in pain. I am doing Iodine and nutritional supplement support and while I have some fatigue am feeling better and stronger every day. And I must add drug free body for the first time in my life. I would not recommend going off this without the aid of a NDs support and direction as I tried going off it years ago and had to go back on. This time the ND gave me specific instructions which made it easier.

  21. I have been on levothyroxine or levoxyl for 30 years, my GP recently reduced my dose to almost 1/2 – I was exhausted, weight gain, etc. My endo has increased dose, I feel better already. I believe most of the side affects are due to my thyroid not the medication. I feel one thousand times better on levoxyl.

    • I agree. Why is everyone blaming the medication? The above side effects are all that of hypothyroidism. Obviously it’s not the correct dose for them. I’ve been on the lowest dose of Levo for only a month and it’s night and day improvement from before taking it!

      • Tracy, not everyone responds the same to drugs. If you develop new symptoms upon beginning a medication, then common sense dictates that these new symptoms are due to the medication.

      • I’m only on 50mg. I did not have any symptoms before I started. They found out that I was hypo from a routine blood test. Now all my bloods are perfect they say. I’m not. I’m off work sick. Anxiety, I cant walk far (too weak legs), every time I move I’m breathless, constant blurred vision. Sweating. My doctors are adamant that it’s not the levo.

  22. I can safely say that Synthroid has very nearly ruined my life. I’ve been on it since 2005 when I had lobectomy due to a multi-nodule goiter. Particularly in the last few years, the mood swings have been devastating.

  23. Even though I have been on synthroid for 2 years and have experienced many or all of the above symptoms, I still feel better than before I started taking it. I tried levothyroxine (generic form) which did not work at all and the above symptoms were skyrocketing! When I called my doctor complaining about my mood(raging!) and swollen face and hands, she didn’t take me seriously.

    Upon doing bloodwork, the TSH levels had risen considerably just during that trial period and we switched to synthroid. I feel so much better and yes the side effects can feel uncomfortable, I feel the improvements outweigh these side effects. Nothing in life is perfect!

  24. Synthroid is an awful medicine. I do not take any other medication, started synthroid almost 6 mos. ago. I have Hashimotos, felt way better when I was taking nothing. I am miserable on this medication. I have told my Dr. about these side effects I am having, he says “these are not side effects of Synthroid”. I am seeing a Holistic doctor next week and I believe I will try something more natural.

    • I would like to hear your results of that meeting too. I hate synthroid. I have only been on it almost three months, and have changed the dosage three times. Hot flush / flashes in my face are too much. Tomorrow I will not take anything, and try to calm this stuff down in me.

  25. T4 only treatments like Synthroid won’t help the majority of patients and this has been proven by the best thyroid doctors and researchers in the world. T4 is useless if your body can’t change the T4 to T3 or if you have thyroid resistance–where T3 can’t get to your cells. The “side effects” here are all known hypothyroid symptoms, so other than bring your temperature up a bit and lowering your TSH, it’s doing a heck of a lot of nothing.

    You may look better on a blood test but the damage that hypothyroid does to your body continues. T3 or natural desiccated thyroid is what works but you may need to see an Integrative doctor to get it. Please check out a documentary coming out–Sick To Death! (Sick2Death. Facebook-petitions to sign there and patients confirming that Synthroid didn’t help them) and some of the better thyroid sites like Stop the Thyroid Madness, Hypothyroid Mom, and keep in mind that this disease runs in families.

    This is a fight for better medical training, treatment of thyroid disorders. Our kids may go through the same thing. Mine have.

  26. I had a thyroidectomy 22 years ago and have been on synthroid ever since. I tried the generic once and found it to be totally ineffective and went back to the branded. I experience nearly ever side effect listed now. For some reason the anxiety, heart flutters and palpitations seem to be more bothersome now than ever.

    I seem to have less tolerance for things than ever before. Now I read blogs all the time and see so many people deal with same issues in do. Lots of different directions we can go in. I am at a point I cannot deal with this on my own any longer. I am not myself anymore. I need to get back to my old self ASAP.

    • So sad to hear this, Ken. It truly changes personality, this medication, is not it so? I cannot recognize myself either – it feels like I am not myself anymore. I experience all the side effects mentioned above, all of them. I need help too, but there is no help. I love to help to other people, but, when it comes to myself…

      I guess that there should be way to manage this, some natural way. In your case, there is at least an excuse why you started to take this so-called medication, in my- no. I stupidly trusted to my family doctor, who told me that I have to take it. No, I am on this medication for 22 years. I wish form the button of my heart for you to find some help and to be yourself again.

    • I too had a thyroidectomy (papillary carcinoma) 27 years ago and fluctuated between Eltroxin and Synthroid all of these years. I have most of these side effects and they are only getting worse with time, especially the anxiety and heart arrhythmia (extra ectopic ventricular beats was the diagnosis 15 years ago). Now my heart seems to skip a beat every 10 beats or so, very disturbing.

      Memory and cognitive ability is suffering with increasing severity. I need assistance to figure all of this out. The info seems to be aimed at people with thyroids that are not working properly, but what about us without a gland?

      • Cynthia, I also do not have a thyroid gland. Are you on Facebook? There is help, but you have to do a lot of research. IF you are on FB, I suggest look up Living Without A Thyroid on Synthetics… there is a lot of info there. Have you had a reverse T3 test done? The problem is, you have to become as astute as your doctor.

        If your Reverse T3 test is too high, this can be a reason for all of your symptoms. Many do not do well on T4, or thyroxine alone… T3 must be added. T3, otherwise known as Cytomel. Another site which can help, but I am not a huge fan is FTPO or STTM. Stop the Thyroid Madness.

        I am not all for NDT, or natural desiccated thyroid, but they are not for Synthroid at all and with good reason. Many are sick on it. T3, especially for those without a thyroid, need T3… that is a fact. T4 made my heart feel like it was going to explode. I had to get off of it.

  27. I have been on thyronine for last one year. Though my dosage is very minimum I experienced extreme constipation if taken before food. When I shifted it’s intake after food, practically there was no adverse side effects except that the dosage seems to be slightly low. But I know I don’t need the next higher dose. I’m on Eltroxin 25 much.

  28. In my twenties I began taking synthroid and had a TSH level of 3.2. I experienced insomnia and after 6 months stopped taking it. Levels were rechecked a year later after being off and my TSH level rose to 9.5 (extreme hypothyroidism). A similar experience happened when taking vitamin D and testosterone. After cessation, levels plummeted to much lower than they were before. Does the body withdraw from making hormones or vitamins when you artificially administer them?

    • Oh, my….!! And you do think that your TSH is high!? I never ever would have taken synthroid, if my TSH would be, say, 3,2 or 9.5!! Never ever! My TSH is 42 and even then I do no want to take this dangerous medication. I better would lived 3 days normal than 33 years with this so-called medication.

      I very much regret that I listened my doctor and began to take it. Then, many years ago, I did not check anything, I did think about anything. I just did not question of my family doctor is right or wrong, I just took the dosage she prescribed.

      No one told me, that, if we start to take this medication, we have to take it for the rest of our lives. I experience all the side effects above! All of them! When I started to pay an attention to them… it is too late, a damage is done.

  29. I have not had one side effect improve in 3 years. I put on 20 kilos which has effected my bulging discs in my back in a major way. Exercise does not remove any weight. I have had major hair loss once each year. I am so tired all the time and my depression and anxiety are in a dangerous place.

    Do I want to go on like this for the rest of my life? I don’t. My endow is a waste of space, even tried to blame the weight gain on depression medication which I have been on all my life with no side effects. I was 58 kilos, now 78.

  30. YES! I still have the majority of these symptoms! I have been on this drug for over 2 years. I thought that I might have Lupus because of the sore joints, weight gain and round face. WOW, I will be calling my doctor tomorrow to talk about this. Now I know I’m not crazy!

    • I am furious…with myself for not researching this med before taking it. I have been on it for several years and have been experiencing the majority of the above side effects… I do know once you are on it there is no way of going off it!!!

      • Teri, Many doctors and pharmacists will tell you that you can’t go off Synthroid once you start it, but depending on the dose, some doctors will say it’s okay to stop. Four years into treatment, I was told to increase my dose. At the time, my doctor said she doesn’t believe that a patient has to be on Synthroid for life.

        Following the increase, the side effects became unbearable (the overheating which resulted in daily migraines, not to mention bloating, hair loss, dry skin, dry mouth, etc.). I stopped taking the medication altogether about three months ago. I don’t feel more fatigued for being off it, but some of the side effects are completely gone!

        Maybe another doctor, or a Naturopath could help you find a better treatment option for your hypothyroidism. (I also tried the Natural Dessicated thyroid treatment, but after awhile the side effects were terrible). All the best to you!


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