How Long Does THC Stay in Your System?

It’s impossible to predict with 100% accuracy how long it will take after using cannabis for you to pass a drug screen unless you take a home drug test beforehand. Here’s some information about cannabis drug tests and how you can figure out whether you’ll pass one.

How Your Body Processes THC

When you smoke marijuana or use a weed product, THC is absorbed into various tissues and organs in your body, including your brain, heart, and fat. It is also metabolized by your liver. 

About 65% of cannabis is excreted in your poop and 20% leaves through urine. The rest is stored in your body.

Eventually, the THC that’s stored in your tissues is released back into the bloodstream so it can be metabolized by your liver. When you use cannabis frequently, THC builds up in your fatty tissues faster than it can be removed, so the compound can show up on a drug test for some time afterward.

But how long does it actually take before you can pass a marijuana drug test? There is no one size fits all solution.

What Factors Determine How Long THC Can Be Detected?

It’s hard to estimate exactly how long after using THC it will take to pass a cannabis drug test. Here are some factors that influence when your body will be free from THC.

Frequency of Use

Cannabis builds up in your system over time, so it takes much longer for daily or frequent users to test negative for weed. It can take just a few days for THC to leave your system if you smoke one time, but it can take a month or more if you’ve been smoking every day for years.

In addition, the timeline in when you last used THC is also important. Taking a break from using cannabis prior to a test may help your chances of passing.


Some factors that determine your metabolism include:

  • Muscle mass
  • Age
  • Sex
  • Genes
  • Physical activity
  • Smoking

Body Fat Percentage

THC can bond to fat molecules in your body, causing it to stay in your system for longer. If you have a higher body fat percentage, you may metabolize cannabis more slowly. Women may also eliminate marijuana from their system slower because of their body fat composition.


When you’re dehydrated, your body has higher concentrations of THC. Drinking a gallon of water probably won’t make the difference to pass a cannabis drug test. In fact, it may dilute your sample so you have to retake it.

Delivery Method

How you consume cannabis may impact your detection time. Weed edibles take a long time to leave your system. Vaping or smoking marijuana causes THC levels in your body to go down faster.

THC Detection by Test Type

So now the moment of truth. How long before you can pass a THC drug test? Well, it depends on the type of drug test that’s being administered.

Blood or Saliva Drug Test

Blood and saliva cannabis drug tests are very rarely used, especially for employment screenings. This is because THC doesn’t stay in your bloodstream for very long. However, blood and saliva tests may be used to check your current level of impairment. You might encounter them after a car accident or at a roadside sobriety checkpoint. 

One study found that THC was found in smokers’ saliva up to 72 hours after last use, but generally, as long as you’re not high at the time of the test and you haven’t smoked that same day, you should pass.

Hair Drug Test

You might encounter a drug test that checks your hair follicle for evidence of cannabis use. Cannabinoids reach the follicle using small blood vessels, as well as sweat around the hair shaft.

Hair drug tests are the most sensitive option. Since hair grows about half an inch per month, a 1.5 inch hair segment taken close to the scalp can detect daily or near-daily marijuana use for up to 90 days. However, they’re not very reliable to detect infrequent cannabis use, so they’re not very commonly utilized.

Urine Drug Test

Urine is the most common way to test for marijuana. It takes a visual and chemical examination of a urine sample to determine whether drugs are in your pee using its metabolites. It does not test to see whether you are currently under the influence of cannabis.

Urine drug tests are used for employer, government, and probation testing because they are easy to administer, and you can get the results in as little as 5-30 minutes. They’re also affordable. You can purchase drug tests to use at home to check your cannabis levels before you go into the lab.

A general guideline for how long it takes to test negative for cannabis is:

  • Single use: 3 days
  • Moderate use (four times per week): 5-7 days
  • Daily use: 10-15 days
  • Heavy use: 30 days or more

Keep in mind that these numbers can vary dramatically based on the factors listed above.


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