How Long Does Weed Stay in Your System?

Green Marijuana Leaf and Pink Human Lungs on White Background


Tetrahydrocannabinol (THC), the psychoactive element in marijuana, is the chemical that makes people feel "high”. It can linger in the body for days or even weeks after ingestion.

The laws of its legality are constantly changing. So, before reading further, take a look at this map of marijuana legality made by the DISA to find out the current status in your state.

Many variables determine the length of time THC remains in the body or shows up in a drug test, including, body fat, consumption habits/drug usage, and sensitivity to drug tests.


Let’s get to it:


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What happens when you take marijuana?

Hippy Girl Smoking Weed and Wearing Sunglasses on Light Blue Background

The primary psychoactive ingredient of cannabis, tetrahydrocannabinol (THC), accumulates in fat tissue.Then it slowly diffuses back into your blood, making it a fat-soluble chemical. In other words, it binds to fat in the body, which means it takes more time for your body to eliminate THC.

As for body tissues retaining THC, these are released into the bloodstream over time. Afterward, the liver metabolizes them. For heavy users, THC accumulates in fatty tissues quicker than it can be removed. This implies that a heavy smoker might test positive for marijuana usage days after quitting

Marijuana detection windows

According to research, marijuana detection windows are identified based on how often a person smokes. It explains:

  • For someone smoking weed for the first time, tests may detect it for about 3 days.
  • For occasional marijuana smokers, cannabinoids remain detectable in the urine for up to 7 days.
  • For chronic users, cannabinoids may be detectable for longer than 21 days (when tested using the standard cutoff concentrations).

The kind of test a person takes is also a determining factor in marijuana detection windows. According to Medical News Today, the following are estimates of detection windows for marijuana tests:

  • A urine test can detect THC in the urine for about 3–30 days after use.
  • A saliva test can detect THC for about 24 hours after use. Some tests, though, have detected marijuana for up to 72 hours.
  • Hair tests are the most sensitive tests that can identify THC up to 90 days after consumption. These tests test for oil in the skin that transfers to the hair. Thus they may occasionally provide a false positive
  • Blood tests can only detect THC for 3–4 hours.

Another study showed that non-smokers exposed to marijuana could come back with a positive test. Trials didn't show positives for tests with a 75 or 100 ng/mL cutoff level. But they did successfully detect THC with 50 and 20 ng/ml cutoff level drug tests.

They also mention that secondhand marijuana smoke "demonstrates that extreme cannabis smoke exposure can produce positive urine tests at commonly utilized cutoff concentrations. However, positive tests are likely to be rare, limited to the hours immediately post-exposure, and occur only under environmental circumstances where exposure is obvious."

In that case, if you aren't smoking marijuana, stay a distance or entirely away from smokers. Not because you hate them, of course, but to avoid getting a positive test.

Factors that influence detection

It's better to play it safe when it comes to cannabis consumption before a test. That's because it's difficult to know how long cannabis will stay in your body. Several factors play a role in whether a drug test detects marijuana, including:

Test cutoff level

Depending on the test cutoff level, it can detect even low consumption of marijuana. Types of drug tests can include blood, urine, hair, and saliva.

THC dose

THC, not marijuana, is the focus of marijuana drug testing. As a result, the amount of THC consumed by a person is a critical component. THC has a cumulative effect. So, someone who smokes multiple times over several days has absorbed a higher THC dose. Thus they are more likely to test positive than someone who only smokes once.

Each THC dosage and potency is also essential. However, it can be tricky to determine the strength without sensitive laboratory equipment. The experience of being "high" is also unreliable due to several things other than THC dose amplifying or lessening this sensation.

Body fat

People with more body fat may metabolize marijuana more slowly than those with less body fat since fat stores marijuana. 

The body mass index (BMI) is one method of determining body fat. Nonetheless, you shouldn't rely on BMI alone. That's because the more muscle mass you have, both BMI and weight will rise. 


THC concentrations in the body rise as a result of dehydration. While drinking a lot of water is unlikely to impact a drug test, being very dehydrated might significantly.

THC levels will vary throughout the day, depending on your hydration levels. Morning urine is generally more concentrated than late afternoon urine. In other words, you'll be able to see higher levels when tested at different times on the same day.

For that reason, if you're preparing for a urine THC test, use an at-home test and take the first urine as a sample. Then you can be sure whether your body is completely clean from THC.

Exercise & metabolism

A 2013 study examined 14 regular cannabis users. The researchers asked participants to exercise for 35 minutes on a stationary bike. The purpose of this study was to explore the impact exercise had on THC levels. The results revealed that cardio might backfire on people who want to get THC from their bodies.

This fat-inducing workout showed how the body metabolized THC. Researchers also asked participants to refrain from marijuana the night before the experiment. This would be to avoid any high levels in the body and potentially skewed results.

Once participants finished their exercise, researchers saw a spike in THC. Even though levels were low before starting the experiment. Along with high THC, free fatty acids were also spotted in the blood, which showed that the workout did indeed burn fat.

The researchers concluded that THC levels in participants' bodies were still high enough to be seen on drug tests. This is important to keep in mind for anyone looking to pass a roadside or employer drug screening.

In addition, two hours after working out, the THC spike seemed to fade away. So, people interested in ridding their bodies of THC via exercise should do so a couple of hours before taking the test.

"Fasting is going to burn fat, which is going to release more cannabinoids," Ryan Vandrey, associate professor of psychiatry and behavioral science at Johns Hopkins University, explains. "If you have more fat, then there is more tissue for the cannabinoids to get stored in, so you might get a little bit longer window of detection."

All in all, exercise should not be your go-to method if you'll be taking a THC test soon. Instead, cut some fat and hit the gym regularly until your next test.


Concerning body fat, metabolism may play a huge role in THC detection. The slower the body takes to completely metabolize THC out of the body, the more likely it is to show up on an upcoming test.

How to get marijuana out of the body faster

The best method is to stop ingesting any marijuana completely. However, there are a few home remedies that could also help. For example, cranberry juice or lemon water may flush out any toxins from your body.

Also, proper hydration may help pass a drug test. The less hydrated you are, the more concentrated the urine is, increasing your chances of a positive result. Ultimately, the period between the previous exposure and the testing is the single most crucial element.

How much do you have to smoke to fail a drug test?

Hand With a Magnifying Glass Looking at the Cannabis Hemp Leaf on Yellow Color Background

It's tricky to determine precisely what the quantity of THC is in any given amount of marijuana. Research has not yet covered the amount of weed a person must consume to fail a drug test. That may be due to the differences in BMI, frequency of use, etc., between participants.

One commonly found point amongst studies is that the more you ingest weed, the more likely you will fail a drug test. 

The 2017 study reported that from 136 marijuana users, 77% percent of heavy users and 39% of light users produced positive tests. But, no non-users had positive test results. This also suggests that false positives when performing hair tests may be rare.


There is no set time it takes THC to leave your body entirely, nor can it be 100% accurate all the time. Many factors influence this, including the quantity of THC in the marijuana, your BMI, hydration levels, etc. Thus, it's best to prevent detection on a drug test by taking the necessary steps to ensure you rid your body of THC remnants. Home tests are a quick and easy solution to solidify that your body is free of THC.

Furthermore, another study has shown that a non-smoker who is exposed to other people who smoke marijuana can come back with a positive test. Trials made however, did not show positives for tests with a 75 or 100 ng/mL cutoff level, but they did successfully detect cannabis with 50 and 20 ng/ml cutoff level drug tests.

They also mention that secondhand marijuana smoke "demonstrates that extreme cannabis smoke exposure can produce positive urine tests at commonly utilized cutoff concentrations. However, positive tests are likely to be rare, limited to the hours immediately post-exposure, and occur only under environmental circumstances where exposure is obvious."

In that case, if you aren't smoking marijuana, stay a distance or completely away from smokers to avoid getting a positive test which can detect marijuana.

Did you find this article useful? We'd love to hear your thoughts in the comments section below!



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Fantastic article!! As states continue to legalize the use of weed. It seems more and more important to understand its effect on the body.

Jen Schreiner

Smoking or ingesting weed on a regular basis can have additional effects on your mind and body. I think we gotta prioritize our health more


I’ve never had Marijuana but I heard from people that weed’s effects appear quickly, usually within 15 to 30 minutes after smoking


It’s great to know more about this. Exercising, eating healthy, and staying hydrated help in metabolizing it faster.

beth pierce

Given that marijuana use is legal in many areas, I really wonder how long companies will continue to test for marijuana use.

Elise Ho

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