Marijuana (Cannabis) is widely regarded throughout the world as the most commonly used recreational drug.  As of 2015, it is estimated that nearly 50% of residents in the United States population have ingested marijuana at some point throughout their lives.  Within just the past several years, recreational marijuana usage has steadily increased.  This increase is largely due to increased social acceptance of marijuana, as well as the drug’s legalization in various states.

Not only can the herb be utilized to treat medical conditions, in some states it is legal to possess and ingest recreationally.  As a result, more people that wouldn’t have otherwise used marijuana are experimenting with the drug to determine whether it offers any medicinal benefit or facilitates a psychological “high.”  The feelings of wellbeing associated with ingestion of marijuana are a result of the primary active ingredient tetrahydrocannabinol (THC) and its ability to stimulate CB1 and CB2 receptors as an agonist.

Most frequent users of marijuana seek out the favorable neurophysiological effects derived from THC such as: increased relaxation (physical and mental) and a mood boost (possibly low-grade euphoria).  Despite the potential psychological benefits of marijuana, one major drawback is the fact that it could prevent you from getting a job or get you fired from your current job.  As a result, many people want to know how long marijuana stays in their system so that they can plan for mandatory drug tests.

How long does marijuana stay in your system?

Even though it may be difficult to abruptly discontinue the drug and deal with the unpleasant wrath of marijuana withdrawal symptoms, quitting is necessary if you want to pass a drug test.  The literature is in conflict when determining how quickly cannabinoids from marijuana are cleared from the body.  Some sources estimate that it takes 25 days, others suggest 11 weeks, and others imply that it takes at least 15 weeks.  In large part, the rate of clearance depends on whether you consider yourself an acute/infrequent user or a chronic/frequent user.

Acute users

For the casual, infrequent marijuana user, it the drug clearance is thought to be considerably quicker than among chronic users.  Researchers suggest that cannabinoids are unlikely to remain detectable at a 50 ng/ml threshold after 4 days.  At a more stringent 20 ng/ml detection threshold, an average one-time user should be able to clear most of the metabolites within 7 days.  This doesn’t mean that the drug is “fully” cleared from the system, but it is cleared to the extent that a person wouldn’t fail a drug test.

Chronic users

Despite rampant conflict within the literature, a review of evidence suggests that for average chronic users, it takes approximately 10 days for clearance of cannabinoids to levels less than 50 ng/ml (a common threshold for drug tests).  If the drug test has a stricter threshold of 20 ng/ml, it could take up to 21 days for an average chronic user to clear enough metabolites to pass the test.  Among outliers (rare cases), reports suggest that it could take up to 60 days for long-term users to clear enough cannabinoids from their system to pass a drug test.

  • Source: http://www.ndci.org/sites/default/files/ndci/THC_Detection_Window_0.pdf
  • Source: http://www.ncbi.nlm.nih.gov/pubmed/3902318

Factors that influence how long marijuana stays in your system

There are many factors that will influence how long metabolites of marijuana stay in your system following discontinuation.  These factors include: dosage, modality of administration, duration / frequency of usage, the specific cannabis ingested, as well as your individual metabolism.  Understand that it is an interplay between these factors that will dictate how quickly your body is able to clear the drug.

  1. THC Dosage (Low vs. High)

In general, the higher the dose of marijuana consumed, the longer the window of detection.  If we were to take two first-time users and give one an extremely high dose, and the other a low dose, the person who ingested the extremely high dose would test positive for marijuana longer after cessation than the individual that ingested the lower dose.  Most users prefer to smoke between 0.1 grams and 0.75 grams for intoxication.

Dosage of “marijuana” is somewhat misleading because an individual could smoke a smaller amount of a highly-potent (30% THC) plant and end up with the metabolites in their system for a longer duration than someone who smoked more of a less-potent (10% THC) plant.  Therefore it is important to consider the density of THC within the plant that is smoked when attempting to determine how long it will remain in your system.  THC metabolites are what need to get eliminated from the body in order to pass a drug test; the less THC – the quicker the clearance.

  1. Frequency/Duration of Usage (Acute vs. Chronic)

There are four general permutations that could be made when considering both duration of usage and frequency.  These include: short-term/infrequent users, short-term/frequent users, long-term/infrequent users, and long-term/frequent users.  Based off of these generalized permutations, the individuals who ingested marijuana with the greatest frequency and duration are likely to have the most difficulties with clearance; in these users the presence of marijuana within the system may linger.

This is due to the fact that the cannabinoids continue to accumulate over a long-term.  Plus, long-term/frequent users generally have built up some degree of tolerance to the drug and are likely to ingest higher dosages (which was already mentioned to affect elimination).  On the other end of the spectrum, short-term/infrequent users will find that marijuana metabolites can clear from the system within several days.

The long-term/infrequent users may not need to worry as much about clearing marijuana from the body, but the frequency matters.  A person who has smoked for 10 years, but only once every 3 months will likely have an easier time clearing the drug from their system than someone who has smoked for the same total duration (10 years), but once per month.  Frequency of usage likely matters more than the cumulative time span over which one has smoked, but both are factors that influence how long the drug is detectable within your system.

Frequent usage of marijuana results in storage of THC metabolites within body fat at a rate quicker than they can be eliminated.  The more frequently a person uses, the greater the accumulation of these metabolites, resulting in a prolonged elimination “half life.”  For this reason, frequent users of marijuana often fail mandatory drug tests; overestimating how quickly they can eliminate THC from their body.

  1. Modality of Administration

The modality of administration (or ingestion) of marijuana will influence how THC gets absorbed, and ultimately how quickly it clears from your system.  Understand that there are many ways in which marijuana can be ingested including: inhalation (smoking or vaporizing) and oral ingestion (capsules, edibles, etc.).

Inhalation:  Smoking marijuana is the quickest way to absorb the THC, with blood levels peaking between 9 and 10 minutes into a smoke session.  The amount of THC can be modified based on how deeply someone inhales while smoking.  Those who inhale as deeply as possible maximize the chances of increased THC levels (and increased intoxication), compared to those who take shorter inhalations.

Among first-time marijuana smokers, THC blood levels are thought to plummet by nearly 60% after just 15 minutes following their last puff.  In some cases, THC levels in drug-naive individuals will plummet below detectable levels within just 3 to 12 hours following a smoke.  Keep in mind the numerous factors such as: depth of inhalation, number of puffs, etc. – that will influence how quickly THC is cleared from the body after smoking.

Oral ingestion: Eating marijuana in the form of “edibles” is thought to yield peak THC blood levels within 1 to 5 hours post-ingestion. The peak in THC blood levels may depend on the way in which the THC is prepared (and the strength); certain oral formulations may prove superior in terms of absorption.  Among drug-naive users, blood levels of THC plummet significantly after 25 hours post-oral ingestion.

However, the THC metabolites are often present in excess of 50 hours post-oral ingestion.  As a result, it likely takes the body longer to clear orally ingested marijuana than inhaled (smoked) marijuana.  Long-term consumers of “edibles” therefore may have greater difficulty clearing the drug from their body than long-term cannabis smokers.

  1. Individual Factors

When contemplating how long marijuana is likely to stay in your system, it is important to consider individual factors that could influence its clearance.  Although these individual “lifestyle” factors aren’t likely as influential as frequency/duration of use or dosage – many users fail to consider their impact on total detoxification.  Various individual factors that will have influence over THC clearance include things like: metabolism, dietary intake, whether you’re using other drugs (or supplements), how often you exercise, and sleep patterns.

  • Metabolism: The most notable factor discussed by researchers is your metabolism.  Individuals with a fast metabolism are often able to clear the drug from their system at a much quicker rate than those with slower metabolisms.  If you happen to be an individual with an exceptionally slow metabolism, it may take much longer than average for your body to convert THC to the inactive “THC COOH,” and ultimately clear this metabolite from your system.
  • Height/Weight/Fat: It is important to consider that height, bodyweight, and percentage of body fat may influence speed of THC metabolite clearance from your system.  Individuals with an above average percentage of body fat may have a more difficult time eliminating THC metabolites.  Furthermore, individuals that ingest less marijuana in relationship to their size (height and weight), may be able to clear the drug quicker than those who ingest a greater amount in relationship to their size (height and weight).
  • Other drugs / supplements: You may want to consider that using other drugs and/or supplements may serve to slow the clearance process or expedite it.  When certain drugs are used simultaneously with marijuana, it is important to consider that your body will need to clear itself of multiple exogenous substances (rather than solely marijuana).  As a result of multi-drug usage, the detoxification process may be slowed in certain individuals.  On the other hand, certain supplements are thought to be beneficial in expediting clearance of marijuana.
  • Lifestyle: Other factors that can have a profound influence on the efficiency by which your body detoxifies include: dietary intake, stress management, exercise, and sleep.  Those eating unhealthy foods with high stress lifestyles, minimal exercise, and poor sleep – may not clear marijuana from their system very quickly.  On the other hand, someone eating an optimal diet, maintaining low stress, getting exercise (to speed the metabolism), and proper sleep (which also affects metabolism) – may find that THC metabolites clear quicker than average.

Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2689518/

How long does it take to clear THC from your system?

Since most of the psychoactive effects of marijuana are a result of tetrahydrocannabinol (THC), it is the THC and metabolites that are assessed on drug tests.  As a result, most people want to know how long it takes for THC to fully clear from their body.  Upon ingestion of marijuana, THC levels peak at different speeds based on the modality of administration, as well as other individual factors (mentioned above).

Someone who smokes marijuana may find that THC levels peak within approximately 10 minutes, whereas someone who orally consumes marijuana (e.g. “edibles”) may find that THC levels peak within 5 hours.  Among those who smoke marijuana, blood concentrations of THC tend to rapidly diminish following the smoke session due to the fact that it is dispersed throughout various bodily tissues and metabolized by the liver.

Since THC is considered “fat soluble,” it is absorbed by organs that facilitate the circulation of blood including: lungs, heart, brain, and liver.  These organs often retain THC and various metabolites for a much longer duration than the bloodstream.  Regular users of marijuana can expect that THC may stay within their fat tissues for approximately 4 weeks.

The liver is primarily responsible for metabolizing (breaking down) THC, but other organs such as the lungs and brain may aid in the process.  For most users, between 80% and 90% of THC is cleared from the system within 7 days.  Some believe that the majority of THC metabolites are excreted via feces (60%), whereas 20% are cleared via urine.  Keep in mind that speed of THC clearance is subject to significant individual variation.

What is the half life of THC?

Most drugs have a relatively straightforward elimination half life.  Half life refers to the amount of time it takes for half (50%) of the drug to be eliminated from the body.  Due to the fact that THC doesn’t dissolve well in water, and is stored in numerous fat cells, it has a relatively prolonged half life.  It is estimated that the half life of THC is approximately 3 to 4 days following ingestion.

In other words, for certain people it takes between 3 and 4 days for 50% of the THC to clear from the body.  However, the half life for THC is subject to significant individual variation and cannot be considered universal.  Factors that influence the half life of THC include: dosage, frequency of use (it accumulates in fat cells with greater frequency), and metabolism.  For certain individuals, the elimination half life of THC may extend beyond 10 days.

Since the elimination half life of THC is not universally predictable, it is recommended to abstain from smoking as long as possible prior to a drug test if you hope to pass.  Keep in mind that assuming the half life of THC is 3 days for one person, this means that it would take up to 17 days for complete clearance of the drug.  If the half life for another person is 10 days, it could take nearly 2 months to completely detoxify.

Different types of drug tests to detect marijuana (THC)

There are a multitude of drug tests that can be administered to determine whether someone has recently used marijuana.  These tests involve collecting some sort of sample from an individual including: saliva, urine, blood, or hair.  Following sample collection, they are analyzed to determine whether an individual has heightened levels of THC metabolites.

The levels of these metabolites are reported in the format of “nanograms” (billionths of a gram) per milliliter (ng/ml).  For certain tests, the “threshold” of THC metabolites is set at 50 ng/ml, while for others it is set at 20 ng/ml.  If you are a regular user of marijuana, it will take much longer to pass a drug test with a threshold set at 20 ng/ml than one set at 50 ng/ml.

Urine tests: The most popular and accurate way to test for the presence of marijuana is via a urine sample.  Fresh urine samples are collected from individuals and assessed for the presence of “THC-COOH” (an inactive THC metabolite).  Most urine samples are set at the 50 ng/ml threshold and should someone test positive, the results are often confirmed with GC/MS (Gas Chromatography / Mass Spectrometry).

Most urine tests are able to accurately able to determine whether an individual has used marijuana within 1 to 3 days.  Metabolites tend to show up after just 2 to 5 hours post-marijuana ingestion.  The accuracy of urine tests may decline after a week, but many regular (or heavy) users will test positive after weeks of abstinence.

  • Single-time user: Your average single-time user may test positive via a urine test for up to 7 days after cessation.
  • Moderate user: An average moderate user may test positive on a urine test for up to 14 days (2 weeks) after cessation.
  • Regular user: An average regular user may test positive on a urine test for up to 21 days (3 weeks) after cessation.
  • Heavy user: Those that consider themselves heavy marijuana users may test positive for up to 60 days (in some cases more) after cessation.

Hair tests: These types of tests involve collecting the most recent outgrowth of hair (1.5 inches) from an individual, which is then analyzed to determine whether THC is present.  Should a person have extremely short hair, the ability to detect THC may be compromised.  However, should an individual have very short hair, sometimes body hair will be used as a sample.  Body hair grows at a slower rate than scalp hair, and as a result, it provides a lengthened detection window.

Test results remain unadulterated even with usage of hair products (shampoos) and even chemicals (bleach).  If you used marijuana recently and are subject to a hair test, it’s not worth trying to manipulate your hair to pass the test.  That said, hair samples can detect 1 pg/mg of THC – meaning it only takes a small amount to test positive.  Though hair tests are not as common as urine tests, it is simple to collect, store, and transport hair samples.

It is estimated to take 7 to 10 days post-cannabis ingestion for “positive”-testing hair to grow above the scalp.  Despite the fact that hair tests will not detect recent marijuana usage (within the past 7 days), they are able to detect usage for up to 90 days (3 months) following last ingestion.  Since THC does not always reliably bind to hair follicles, hair testing may be subject to inaccuracies.

Saliva test: In some cases, individuals may be subject to a saliva test.  Saliva tests are considered newer, and aren’t usually as reliable as urine tests.  The lack of reliability stems from the fact that there is a short window of detection for cannabinoids within saliva.  Furthermore, only minimal amounts of the drug are excreted via saliva, making it difficult to accurately determine whether someone had ingested marijuana.

Generally a saliva test is capable of determining whether someone had used marijuana within 1 to 2 hours post-ingestion.  Should the testing be conducted within an official laboratory, the threshold level may be 0.5 ng/ml – and could be detected up to 3 days post-ingestion.  Despite the accuracy of saliva tests in determining whether someone had recently used marijuana, they aren’t very good at detecting usage that occurred several days prior to testing.

A non-laboratory saliva test may incorporate a less stringent threshold at 25 ng/ml and may only be able to detect the drug for up to 12 hours following usage – making the test relatively useless.  Additionally, some speculate that the swishing around of certain fluids within the mouth may serve as a way to manipulate saliva test results.

Blood tests: Since blood tests aren’t well-tolerated and difficult to administer, they are seldom used compared to urine tests.  Blood tests generally determine whether there is a high level of THC within the blood.  In most cases, blood tests are used by law enforcement agencies to determine whether someone had been driving under the influence of marijuana and/or other drugs.  They may also be utilized by professional organizations to test top-level athletes.

Most employers will not subject their employees to a blood test to determine drug usage.  That said, an individual may test positive on a blood test for marijuana within 2 to 3 days following ingestion. Among frequent users, blood tests are generally able to accurately detect marijuana metabolites for up to 4 weeks.

How long has marijuana (THC) stayed in your system?

Assuming you’ve used marijuana, feel free to share a comment documenting how long it you believe it has stayed in your system.  Discuss the average dosage of cannabis you ingested, modality of administration, duration and frequency of usage, as well as your individual metabolism.  If you were subject to drug testing, mention how long after using cannabis the test was administered, the threshold, as well as whether you passed or failed it.  Do you believe there are any tricks to expedite the clearance of marijuana from your body?