How Long Does Weed Stay In Your System

Weed contains 2 main active ingredients known as tetrahydrocannabinol (THC) and cannabinoid (CBD). Tetrahydrocannabinol accounts for all effects such as sedation, improving mood, altering consciousness and the perception of time and place as well as causing euphoria.

Cannabinoids are sometime linked with a counteracting effect to that of tetrahydrocannabinol, causing slight improvements in memory and cognitive functions. Examples of further names referring to weed include THC, Ganja, Grass, Hashish, Hemp, Indian hemp, Pota and Reefer.

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How does weed work

Weed affects the central nervous system through several mechanisms of action, as follows:

  • In the brain, there are certain receptors known as cannabinoid receptors. After weed administration, weed binds to those receptors, resulting in feeling wellbeing, altering the main functions of those receptors, including concentration, memory, thinking, movement and the perception of time and place.
  • The forgetfulness state and transient memory weakness noticed with weed administration are thought to result from inhibiting the activities of neurons in a certain area in the brain, which is known as hippocampus.
  • Furthermore, weed administration affects another area in the brain known as cerebral cortex, which results in altering the way your body responds to different sensory stimuli, such as touch, sight, hearing, taste, and smell.
  • Medicinally, the main ingredient of weed (THC) is included in a drug known as marinol, which is used to treat 2 disorders, including nausea associated with chemotherapy and to stimulate appetite in AIDS wasting syndrome.

How long does weed stay in your system

Up to 24 days post-administration, weed is likely to stay in your system. The reason is that the half-life of tetrahydrocannabinol ranges from 3 to 4 days, which means that within 3-4 days post-administration, 50% of the administered dose will no longer be active in your system, and so on till the administered dose is fully eliminated.

However, research also report different durations, in regards to how long weed stays in your system, suggesting that it sometimes can take the body around 25 days, 11 weeks or even 15 weeks post-administration to get rid of weed and its metabolites.

Other factors

In addition, there are other factors that can significantly affect how long weed and its metabolites can stay in your system, including:

  • your body mass
  • your age
  • your gender

The administered dose of weed

For example, if you administer an overdose, weed and its metabolites will undoubtedly stay longer in your system. Another important example, if you administer a little amount of a highly concentrated weed, that will undoubtedly take longer time and produce a higher percentage of weed metabolites in your system, compared to another person administering a higher dose of a diluted weed.

Whether you’re a light or a heavy weed user

How many times do you administer weed daily? Or, weekly? Or, monthly? Surely, that has an impact on how long weed stays in your system.

If you’re a light weed user, in order to pass a drug test that detects as less weed as 50 ng/ml in your system, it can take your body around 4 days post-administration to show negative. If you have administered weed only once, it’d take your body around 7 days to show negative in a test that can detect as less weed as 20 ng/ml.

If you’re a chronic weed user, weed can stay detectable in your system for a longer duration. Generally, your system would need around 10 days to pass a weed test that detects as less weed as a 50 ng/ml concentration; and up to 21 days, if the test is valid to detect as less as 20 ng/ml concentration.

Metabolic rate of drugs

It determines how quickly your system is able to get rid of weed and its metabolites. That majorly depends on the functioning ability of your system, including your liver.

Route of administration

The route through which you administer weed also affects how long weed stays in your system. Weed is commonly administered orally or through inhalation. Each route of administration determines how much weed is absorbed, how much reaches your blood stream and different body parts, how much is metabolized, and how quickly metabolism occurs, and thus how much weed would be detectable during drug tests.

Body fat

Weed and its metabolites have a high tenancy to be stored in the fatty tissues of the body. Those tissues act like a reservoir of weed, which results in significantly prolonging the duration weed affects the body and stays inside the system.

Therefore, the body fat content determines how much weed is stored in the system, which means that people with a higher content of fats, such as obese people, are much likely to store weed for longer time, compared to people with normal or less fat content.

Physical workouts

Physical workouts cause the body to burn fats, resulting in releasing the stored weed, which in turn rises in blood, saliva, hair and urine. Therefore, physical workouts can have a dual effect on the results of weed’s tests, as follows:

  • If you exercise regularly a long duration post-administration and before drug tests, that’d help your system get rid of the stored weed, with a higher chance to pass drug tests.
  • If you have just exercised before undergoing drug tests, that’d make weed much likely to show positive.


The more hydrated your body is, the more you are likely to pass weed tests. That’s why it’s advised to drink plenty of water after weed administration, and prior to testing, so that your system contains more water content, which would the concentration of weed in your blood, urine and saliva.

Will weed show on a drug test?

YES, weed will show on a drug test, as drug tests are specifically concerned about illicit and addictive drugs, including weed. However, the results of weed tests are much prone to be affected by the factors shown below.

  1. the route of administration
  2. the type of the tests you are required to undergo
  3. the time the test is performed. What a certain test can detect may not be detected by another test at the same moment, as the validity of each test is restricted within a certain time frame.
  4. Individual factors that differ from a person to another, as shown above.

How long is weed detectable


In case of inhaling weed, starting from 9 minutes post-inhalation, and up to 3-12 hours, weed is likely detectable in your blood.

In case of orally ingesting weed, starting from 1-5 hours post-ingestion, and up to 2.08 days, weed is likely detectable in your blood.

However, research shows more concerns, in regards to weed detection in blood.

While some studies show that weed is likely detectable in people administering weed just once within 24 hours post-administration; there is some evidence showing that that duration extends to 2-7 days post-administration in other users administering more than once.

The same with chronic weed users; but, with a longer duration up to 21 days or longer post-administration, as mentioned above.


Starting from 2-5 hours post-administration, and up to 1-3 days, weed and its metabolites are likely detectable in your urine. Urine-based tests are most commonly used for weed detection, as they offer a high sensitivity to detect as less weed as 50 ng/l, within a long period, equating to 7 days for light weed users, 14 days for moderate users, and up to 100 days for chronic users.


Hair-based tests are not effective for weed detection in users administering just once, and less effective in light users, compared to chronic users. Starting from 7-10 days post-administration and up to 90 days, weed is likely detectable in your hair. Furthermore, some sources claim that in case you’re continually and daily administering weed, hair tests are likely to detect weed even for years.

Saliva and fingernails

Saliva is less commonly used for weed detection, compared to hair, blood and urine. Starting from 1-2 hours post-administration, and up to 12 hours, weed is likely detectable in your saliva. That duration of detectability can extend to 3 days, if tests are applied in a specialized laboratory. On the other side, fingernails are not considered for weed testing.

What drug tests will show the presence of weed

  • Blood analysis
  • Urinalysis
  • Hair-based tests, including: Gas chromatography/mass spectrometry, ELISA (enzyme linked immunosorbent assays)
  • Saliva-based tests, such as high performance liquid chromatography (HPLC)

How is weed stored in the body

Within minutes to a few hours post administration, weed is absorbed from your respiratory pathways or gastrointestinal tract, depending on the route of administration. Then, Weed rises in your blood till it reaches its peak plasma concentration.

Within blood stream, weed is distributed to different body parts, with a high tendency to be stored in fatty tissues, prolonging the time weed stays in your system, as explained above. Afterwards, within the previously-mentioned half-lives, the body metabolizes (eliminates) weed and its metabolites from your system, forming different substances through specific types of reactions known allylic oxidation, epoxidation, aliphatic oxidation, decarboxylation, and conjugation.

Weed is mainly metabolized through bile dusts; while just a small amount remains unchanged (active) in the body, and so is excreted in both urine and feces. Weed and its metabolites tend to be stored in hair more than they do in fingernails or saliva. That’s why hair-based test can give an indication, showing whether you are a heavy or a light user of weed. A little amount of morphine-metabolite can stay in your saliva for around 3 day post-administration.


How Long Does Weed Stay In Your System
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Daniel Miller
Daniel Miller

Hey there! I'm Daniel, a 35 years old Ph.D. in pharmacology and a member of THC Detox. My research into cannabis shows how cannabis affects health, including how cannabinoids can be used in the treatment of various diseases. I've got a long list of scientific and medical publications that show the positive effects of cannabis clearly.

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