How Long Does Weed Stay in Your System?


Kelly Weimert

March 14th, 2017

Policy, Top News


With medical and recreational marijuana increasingly legal across North America, it’s raising a number of unprecedented issues around employee and potential employee drug testing.

If you’re using cannabis lawfully then, theoretically, responsible use outside of your work place shouldn’t prohibit you from employment. However, what’s true in theory and in practice are two very different things. Employers are continuing to test workers for cannabis, begging the questions: how long does weed stay in your system? And, is there a safe way to shorten its stay?

First, how do drug tests work?

In order to understand how long marijuana stays in your system, it’s important to be aware of how, exactly, tests for the drug work.

Testing a person’s urine is far and away the most common method, but cannabis can also be detected via hair, blood, and saliva samples. Hair has the longest window of detection — generally about 90 days — while blood and saliva tests only show whether marijuana was used within the past few days.

That said, most employers, when requiring drug testing, will do it through a urine analysis. So, how long does cannabis stay in your urine after use?

The short answer is: It depends.

Marijuana has two primary active ingredients: THC and CBD.

The one most responsible (but not entirely) for marijuana’s psychoactive effects — in other words, the “high” — is THC. Urine tests work by looking for a metabolite of THC called THC-COOH.

THC-COOH is produced after your liver breaks down THC, which allows it to stay in your body much longer than THC.

Most commonly, drug screening companies have a THC-COOH cutoff (the measure that indicates a positive or negative result on the test) of 50 ng/mL, but cutoff levels can range anywhere from 20 ng/mL to 100 ng/mL.

How long these levels of THC-COOH can be detected in your urine depends on a number of factors.

Every individual who uses marijuana metabolizes the drug at a different rate. The amount of daily exercise you engage in, your body fat percentage, and your eating habits all play a role in how quickly THC makes its way through your system, as does the frequency with which you use it.

According to the National Drug Court Institute (NDCI), occasional users of cannabis, or those who try it for the first time, will typically test positive for 1-3 days after use.

Frequent users, on the other hand, should expect to test positive for the drug for 7-10 days following last use. After 10 days, most users ought to pass a test with a 50 ng/mL cutoff.

Still, this is only generally-speaking. Studies suggest that some frequent users will test positive for the drug for up to a month after last use.

So, are there things you can do to rid your body of the drug faster?

There are a number of products on the market aimed at helping people pass drug tests for marijuana. Often branded as “urine cleansers” and “detoxifiers,” some people have found success using them, but none have been proven to work with consistency.

However, some studies indicate that drinking a large amount of water coupled with diuretics several hours before the test will dilute THC-COOH levels in your urine enough to get a negative result.

That said, this method is by no means foolproof, as many drug testing companies are privy to it and will therefore test urine for signs of dilution, which can lead to employment rejection or a person’s having to retake the test.

To put it plainly, depending on your lifestyle, how often you take marijuana, and your body’s individual chemical makeup, cannabis will generally stay in your system anywhere from three days to one month. And while there are certain measures you can take to expedite your body’s processes and combat a positive drug test result, you should keep in mind that none of them are guaranteed to work.

To learn more about cannabis science, sign up for our free newsletter using the form to the right.

Kelly Weimert

About Kelly Weimert

Kelly is a full-time freelance writer based in Austin, TX. A happy hybrid of geek and hippie, when she's not nestled into her couch crankin' out crafty prose with her miscreant Chihuahua, you can find her frolicking outside to keep her sanity in check.


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