How long does Marijuana stay in your system?
Medically reviewed by Carmen Fookes, BPharm. Last updated on Apr 17, 2019.
It varies according to usage
It is impossible for anyone to accurately state the length of time it would take for somebody to test clean for marijuana in a drug test. This is because there are many different variables that impact on the rate that marijuana is both metabolized and excreted (see below).
An estimate of marijuana detection time after last usage is as follows:
|Usage||Estimate of detection time|
|One time only||4-8 days|
|2-4 times per month||11-18 days|
|2-4 times per week||23-35 days|
|5-6 times per week||33-48 days|
|Daily usage||49-70 days after last use*|
*Occasionally, some chronic users with a high tolerance may eliminate THC as fast as a one-time user.
We can give an estimate of the amount of time marijuana remains in the body, but the most reliable way is to test yourself twice weekly until your first, morning urine sample tests clean. However, even this is not 100% foolproof because home drug detection kits have a higher upper limit of detection (usually 50 ng/mL) compared to some other medical testing kits. This means you may test negative, but a laboratory test may still show marijuana in your system.
Note that charts, graphs, or computer programs that claim to be able to predict how long it will take you to test drug-free, are essentially useless at doing this, even though they may say otherwise.
What is delta-9 THC?
Marijuana is produced by the cannabis sativa plant. Cannabis sativa contains over 421 chemicals including 61 different cannabinoids, of which delta 9-tetrahydrocannabinol (delta-9 THC) is considered the most psychoactive. Delta-9 THC has a thick, sticky consistency (somewhere between a solid and a liquid) and is easily vaporized. It readily dissolves into lipids and fats, and once in the body gets deposited in fatty (adipose) tissue, and in the liver, lungs, and spleen.
Delta-9 THC undergoes metabolism in the liver to another psychoactive compound, 11-OH-THC, and then further metabolism to the inactive THCCOOH. CYP2C9 and CYP3A4 are major enzymes involved in this metabolism and both enzymes show genetic variation – this means that some people will metabolize THC faster than normal, whereas others will metabolize it slower than normal.
What variables impact on the time Marijuana stays in your system for?
Individual variables that play a role in how long marijuana stays in your system for and detection times include:
- Body fat: People with more body fat will retain THC for longer. Skinny users have fewer places to store THC.
- Fluid intake at the time of the test.
- Genetics: Fast metabolizers will excrete THC rapidly.
- How frequently you exercise.
- Method and frequency of usage: Infrequent users clear THC faster than chronic users.
- Type of detection test used (blood, hair, saliva, or urine).
- Your general health: Many medical conditions impact on how your body retains, stores, and metabolizes marijuana.
- Other drugs taken: Many drugs interact with CYP2C9 and CYP3A4 enzymes.
- The potency of the marijuana and your tolerance to it can also have an impact.
What are the different ways Marijuana can be tested for?
Firstly, it is important to understand the difference between qualitative and quantitative testing.
Qualitative testing tells you if a substance is there or not.
It does not tell you how much of the substance is there. There will be a cut off point for detection. For example, the Alere DDs 2 Mobile test system used roadside by law enforcement agencies has a cut off level for Delta-9-THC in saliva of 25 ng/ml. Research has shown that this testing system is 97.5% accurate at this cut off (this means that more than 97 people will accurately test positive out of 100 people who have used marijuana in the past 24 hours).
Quantitative testing measures the actual quantity of a substance.
This type of testing is more expensive and time-consuming than qualitative tests and is normally reserved for people who have tested positive in a qualitative test. It needs to be done in a laboratory and is used when a more defined value is needed, say, for prosecution. Quantitative testing can detect minute quantities of a substance, far below the cut off point in a qualitative test. A series of quantitative tests can determine if drug usage is ongoing or has stopped.
The most common ways marijuana can be tested for is in urine, saliva, blood, or hair. Most testing practices look for the presence of THCCOOH which has a much longer half-life (the time it takes for 50% of the substance to be excreted) than delta-9 THC. The half-life of THCCOOH is 20-57 hours in occasional users compared to 3-13 days in regular users.
Estimated periods of detection of the marijuana metabolite THCCOOH
|Test Type||Detection period (estimated)|
|Blood test||36 hours
Some reports suggest up to 7 days with chronic use (>3 months)
|Hair test||Cannot detect first-time drug use in the previous 7-14 days
Every 1cm of hair length represents a one-month window of detection
Detection period depends on hair length but generally 90 days
|Saliva test||Up to 34 hours|
|Urine test||1-4 days
Some reports suggest up to 70 days with chronic use (>3 months)
A false-negative is when the test result is negative for a substance, but the person has been using the substance. A false-positive is when the test result is positive for a substance, but the person hasn’t been using the substance.
Can second-hand marijuana smoke make you fail a drug test?
For kits that detect at the 50 ng/ml level the circumstances would have to be extreme, for example, if you were in a closed car full of marijuana smokers for a couple of hours and you were drug tested the next day. If you are a non-smoker in a ventilated area where other people are smoking marijuana you are generally safe.
Official answer: It varies according to usage It is impossible for anyone to accurately state the length of time it would take for…
Here’s How Long Weed Stays In Your Urine
In honor of 4/20 we’re revisiting some of our greatest…hits.
One of the most common questions people have about cannabis is, “How long does weed stay in your system?” This is a pressing question because there are a lot of employers who require some sort of drug testing. And a failed test could seriously damage your prospects of getting or keeping a job.
The most common way that employers test for cannabis use is by analyzing urine. These tests are fairly cheap and are extremely sensitive to traces of cannabis.
So how long does marijuana stay in your system? How long can weed be detected in your urine? Read on to find out.
THC vs. THC-COOH: The Science Behind Urine Tests
The first thing you need to know is what exactly a urine test is looking for. Surprisingly, they don’t actually detect straight tetrahydrocannabinol (THC). What these tests are really trying to pick up is a chemical called THC-COOH.
When you consume cannabis, THC enters your bloodstream and gets you high. After your body processes the THC it creates a new derivative chemical. And that’s what THC-COOH is.
Urine tests have been designed to detect the presence of THC-COOH since the only way that chemical would be in your body is if you’d already used cannabis.
The problem for pot smokers is that THC-COOH stays in your system much longer than THC. That means that you can test positive for cannabis even if you haven’t smoked for days.
Time Test: How Long Does Weed Stay In My Urine?
OK, now that we’ve got a little science beneath our belts, let’s get back to the big question. How long does weed stay in your urine?
There are a few key factors that determine the answer to that question. How frequently you use marijuana, the size of your dose, and the way your body metabolizes THC all impact how long it’ll stay in your urine.
Since there are so many variables, it can be hard to pinpoint a precise amount of time that THC-COOH will stay in your urine. But researchers have come up with some general timelines that will help you gauge how long your urine will turn up positive for cannabis.
Here’s What the Research Shows
One key study found that weed can stay in a person’s urine for a surprisingly long period of time. That study found that urine will test positive for THC an average of 27 days after use. Heavy users can test positive for as long as 77 days after a smoke sesh.
One-time use will usually stay in your system for 5-8 days.
If you use cannabis 2-4 times per week and then stop, you’ll test positive for 11-18 days.
If you smoke 5-6 times per week, it’ll stay in your urine for 33-48 days.
And if you’re a serious smoker who gets high every day, weed will stay in your urine for 49-63 days.
The Problem With Urine Drug Tests
The obvious problem for anybody who uses cannabis is that you can test positive for a long time after your high has worn off. Think about it: Even if you smoke once and then stop, you can get a positive urine test a full week after you actually puffed.
Critics of drug testing have long pointed out the problem with using urine tests as a way of determining who uses drugs. These critics have pointed out that an employee who lives in a state where pot is legal can follow all the rules and still get in trouble at work when their urine test comes back positive long after they’ve actually sobered up.
Other Types Of Marijuana Tests
Although urine tests are the most common cannabis tests, there are a few others you should be aware of. Some tests look for THC in your saliva — cops use this one a lot. The good news for smokers is that THC doesn’t stay in saliva for very long. Usually, you’ll start turning up positive an hour after smoking and it’ll all be out of your saliva in 12 hours or less.
Hair follicle tests aren’t all that common because they can sometimes come back with false positives. But hair follicle tests can also be the hardest to pass. That’s because traces of cannabis can stay in your hair for anywhere from seven to 90 days.
The last, and least common, test is a blood test. Employers and law enforcement don’t use this one very often since it only detects very recent use. THC-COOH doesn’t bond well to blood cells, so it doesn’t stay in your actual blood for very long.
The Final Hit
If you have to get tested for marijuana, it’s most likely that you’ll be facing a urine test. The problem for pot smokers is that these tests come back positive long after the high has worn off and they’re fully sober.
Since it’s usually pretty hard to cheat a urine test, your best bet is to understand how long THC-COOH will be in your system by using the timelines in this article. The more you can adjust your usage for an upcoming test, the better.
In the end, though, it probably makes the most sense for heavy users to try and avoid jobs that require drug testing. And in the meantime, it’s important for the cannabis community to advocate for the elimination of marijuana drug tests since they don’t actually indicate if a person is impaired while on the job.
Even the most responsible cannabis user will still test positive for days or weeks after smoking. And when that happens they could be disciplined or cut off from a job, even if their cannabis use is legal in their state and it doesn’t affect their work performance in any way.
A version of this article originally appeared onGreen Rush Daily.
(Refinery29 in no way encourages illegal activity and would like to remind its readers that marijuana usage continues to be an offense under Federal Law, regardless of state marijuana laws. To learn more,click here .)
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One of the most common questions people have about cannabis is, "How long does weed stay in your system?" This is a pressing question because there are a lot of employers who require some sort of drug testing. The first thing you need to know is what exactly a urine test is looking for. What these tests are really trying to pick up is a chemical called THC-COOH.