How Long Does Marijuana Stay in Your System?

Although the effects of marijuana fade pretty quickly, that doesn’t mean that it disappears from your system at the same time. In fact, it may linger for up to 90 days depending on the type of weed you used or how frequently you used it. Different components linger longer in different parts of your body, too. So, how long does marijuana stay in your system? Read along to find out as we break down the most important information for you!

The Half-Life of Marijuana

The half-life is a parameter used to measure how long it takes your body to eliminate 50% of a substance you took. It is important because it tells us how fast the entire dose will take to disappear from your system. Usually, it takes substances up to six half-lives to disappear completely since the speed of elimination decreases with time. 

Depending on the type of weed you used, the half-life ranges from 20 hours to up to 13 days. One-time use is usually not detectable after about eight days. It is important to note that traces of marijuana stay longer in different parts of your system. So, the half-life also depends on what kind of test you have undergone and what part of your body was tested.

Blood and Saliva

Marijuana stays in your blood and saliva for only a few hours, which is why blood and saliva tests are rarely used. The only exceptions for this are road accidents or sobriety checkpoints. These tests only show whether you currently have THC in your system. However, if they want to see the level of intoxication, they will need a different kind of test.


Frequent weed use can be detectable in your hair for up to 90 days. However, it isn’t a reliable test for irregular use and it cannot determine the amount of weed used. If you don’t smoke it frequently, you should be able to pass a hair test without much fuss. 


Traces of marijuana stay in your urine for about a few hours. That is why most workplaces use urine tests to determine whether you’ve smoked weed recently. Just as with blood and saliva tests, urine tests don’t show the amount of marijuana you took.

Other Factors That Determine Detection Time

Different factors also affect how long marijuana will stay in your system. These do not depend on the type of testing or the half-life but are more general. 

Body Mass

THC metabolites (what THC is broken down into) are stored in the fat cells of the body. So, the more body fat you have, the slower you’ll metabolize marijuana. Since women naturally tend to have more fat cells, this also means that they often metabolize weed at a slower rate than men. 

Hydration levels

If you are dehydrated, the level of THC in your system will be higher. However, this doesn’t mean that just drinking a lot of water will make THC disappear. It will only dilute your THC levels, but the test will still be positive or just inconclusive, which means you will have to take it again. 


If your metabolism is naturally fast, THC traces in your system will be eliminated quicker. This also depends on your age, whether you exercise regularly, and whether you have some health conditions. 

The Method of Use

Another important factor in detection time is the method of use, or whether you’ve smoked, vaped, or ingested the weed. Smoking or vaping makes the THC levels in your system drop faster. Ingesting weed is a different story. Edibles take longer to break down, so your body retains traces of marijuana longer.

So, How Long Does Marijuana Stay in Your System?

As we discussed above, it depends on a lot of factors. These include the method of testing, frequency of use, as well as factors such as body mass, metabolism, age, sex, and so on. Passing a blood or urine test will only be possible after a certain amount of hours has passed, while hair tests can reveal weed use that is months old. It is important to remember all this before smoking your next dose, so you can enjoy yourself to the fullest while also staying safe and passing any surprise test you might have to take!

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