Drug tests: How long does THC stay in your system?

Drug tests: How long does THC stay in your system?

Even in places where weed is legal, employers can make testing a condition of employment. Get hurt on the job? That makes peeing in a cup almost automatic. Same goes for probation, parole, some sports and even certain types of medical treatment.

Think you might be facing a drug test and need to know how long THC stays in your system? Here's the 411:


Sorry, but no one can give you an exact number.

Unlike alcohol and most harder drugs, marijuana use can be detected long after you last smoked - anywhere from 1 to 90 days depending on the type of test, how often you smoke, how much fat you carry around, whether you have a fast or slow metabolism and a few other things.

The most common type of drug test is a urine screen. It checks your sample for a THC byproduct instead of the kind of THC that gets you high. When you smoke weed, your liver breaks THC down into THC-Cooh and stores this substance in your fat cells where it can stay for a really long time. Over time, the THC-Cooh is slowly released back into your system. That's why the level of measurable THC in your urine can stay steady, or even go up, for a few days after you stop smoking.

You don't have to rid your body of all THC byproducts to test clean. Urine tests measure the number of nanograms per milliliter of THC-Cooh in your sample. Most tests will be negative if they measure below 50 ng/mL, but some cutoff points are as high as 100 ng/mL or as low as 20 ng/mL. Here's how long it takes most people to drop below the 50 ng/mL mark after they stop smoking completely:

  • One-time use: 1 to 8 days
  • Two to four times per week: 10 to 20 days
  • Once a day, everyday: 30 to 45 days
  • Every chance you get: up to 75 days


Cannabis Detection Time: How long does THC stay in your system?

Urine tests are the most common type of drug screen, but there are a couple more worth mentioning.

Saliva Test: THC is almost instantly detectable in your saliva, but it starts to rapidly fade out and is completely gone in 12 to 24 hours. If you're a weed smoker and you have a choice, this is the easiest one to pass. Unfortunately, it usually only used by cops for roadside testing.

Hair Follicle Test: THC takes about five days to show up in your hair, then it can be detected by a drug test for months because the metabolites are stored deep inside the shaft. Because hair grows an average of a half inch a month, most tests use a 1.5 inch sample, measured from the root, to look back 90 days. A shaved head and waxed body eliminates the possibility of hair follicle testing.

Blood Test: This type of drug test looks for actual THC in your blood, but luckily for chronic smokers, THC does not bind well to blood cells. That means your blood is clear almost as soon as your head clears. In most cases, even the heaviest cannabis users will test clean in less than 12 hours after smoking - if they can go that long.


Allowing your body to naturally clear the THC metabolites from your body is the surest way to pass your drug test. You can make this go faster by drinking plenty of fluids, eating a healthy diet and getting plenty of exercise - all things you should be doing anyway.

If you'd like to keep an eye on your progress, you can buy a home drug test kit at just about any pharmacy or order them online. You'll get the highest scores when you first get up in the morning, so that's when you should check. Once you start to test clean at home, give it a few more days to be sure before you take your official test, especially if it will use a lower cutoff point.

Drinking extra fluids before you take your test can help reduce the amount of measurable THC in your urine, but if your urine is found to be too diluted, it will invalidate the test, and that can be considered as much of a fail as testing dirty. Some people use creatine supplements and vitamins to disguise their dilution efforts with mixed results.

Many head shops and health food stores sell products that promise they can flush your system of THC metabolites within hours so that you can test clean. Most rely on dilution and vary in their reliability.

Some people resort to using either synthetic urine or clean urine they've obtained from a friend. As long as they don't get caught and can keep their sample at body temperature, this can work. However, getting caught is considered cheating and will be just as bad as a positive test. If you're taking the test for legal purposes, it could be worse.


Although there are several types of drug tests, urine tests are used more frequently than any other method. No one can tell you exactly how long it will take for your body to eliminate all THC metabolites from your system, but exercise and a healthy diet can speed things up.

Check your progress with home drug test kits and avoid shortcuts like dilution, cleansing products and fake urine.