Marijuana can stay in your system anywhere from 24 hours to 90 days, depending on which type of drug test is used and how often you consume it. A one-time user will typically clear a urine test within three days, while a daily user may test positive for a month or longer. The wide range comes down to how your body stores and processes THC, the main psychoactive compound in cannabis.
Detection Windows by Test Type
Different drug tests look for THC or its byproducts in different parts of the body, and each has its own detection window.
- Urine: 1 to 30+ days, depending on frequency of use. This is the most common test for employment screening. A single use may be detectable for up to 3 days. Regular use extends the window significantly, and heavy daily users can test positive for a month or more after stopping.
- Blood: Up to 12 hours. Blood tests capture active THC rather than stored byproducts, so they reflect very recent use. THC levels in blood peak within minutes of smoking and drop quickly.
- Saliva: Up to 24 hours. Oral fluid tests are commonly used in roadside testing and detect THC deposited in the mouth during smoking or ingestion.
- Hair: Up to 90 days. Hair follicle tests capture metabolites deposited into the hair shaft as it grows, providing the longest lookback window of any standard test.
Urine tests don’t actually measure THC itself. They measure a metabolite your liver produces when it breaks down THC. This metabolite is fat-soluble and lingers in the body far longer than the high does, which is why urine tests have such a wide detection range.
Why THC Lingers in the Body
THC behaves differently from most other drugs because it dissolves in fat. After you consume marijuana, THC is rapidly absorbed and redistributed into fat-rich tissues, including body fat, the brain, and muscle. Over time, your body slowly releases stored THC back into the bloodstream, where the liver breaks it down and you eventually excrete it through urine.
This fat storage mechanism is why detection times vary so much between people. Someone with a higher body fat percentage retains more THC in their tissues, and it takes longer for all of it to be metabolized and cleared. A lean person who uses marijuana once might clear it in a couple of days, while someone with more body fat and a heavier use history could take weeks.
The process also means that frequent users build up a reservoir of THC in their fat cells. Even after you stop using, your body continues releasing small amounts into your blood for days or weeks as fat is broken down through normal metabolism.
Factors That Affect How Quickly You Clear THC
Frequency of use is the single biggest factor. Someone who uses marijuana once will have a dramatically shorter detection window than someone who uses it daily. Beyond that, several other variables play a role:
Body composition. Higher body fat means more storage capacity for THC and a longer clearance time. Research has found that the total amount of THC detectable in blood depends partly on how much body fat a person carries.
Metabolism. A faster metabolism breaks down stored THC more quickly. Age, genetics, activity level, and overall health all influence metabolic rate.
Potency and dose. Higher-THC products deposit more THC into your system, giving your body more to process. A single hit of low-potency flower puts far less THC into fat stores than a heavy session with concentrates.
Exercise. This one is counterintuitive. Moderate exercise on a stationary bike has been shown to temporarily increase THC levels in the blood of regular cannabis users by breaking down fat cells that contain stored THC. The spike was small but statistically significant, and it was more pronounced in people with a higher BMI. Interestingly, short-term fasting alone did not produce the same effect, likely because it doesn’t mobilize fat as aggressively as exercise does. If you’re facing a drug test, working out right before it could theoretically bump your levels slightly rather than help you clear faster.
Edibles vs. Smoking
The method of consumption changes how THC enters your body but doesn’t eliminate the detection risk. When you smoke or vape, THC passes through the lungs and reaches the bloodstream within seconds. When you eat an edible, THC is absorbed through the digestive tract and processed by the liver before entering circulation. This slower absorption means edibles take longer to kick in and can produce a more prolonged release of THC metabolites.
Drug tests detect THC from edibles just as they detect it from smoking, because the liver converts THC into the same metabolites either way. You might expect a urine test to pick up a single edible for roughly a week, and longer with regular use.
How Drug Test Cutoffs Work
Standard urine drug tests don’t flag every trace of THC metabolite in your system. They use a cutoff concentration to separate a “positive” from a “negative.” The most widely used cutoff for initial screening is 50 nanograms per milliliter (ng/mL). If your sample falls below that threshold, you pass, even if some metabolite is technically present.
If the initial screen comes back positive, a confirmatory test is run using a more precise method with a lower cutoff of 15 ng/mL. This two-step process is used in federal workplace testing, including all Department of Transportation safety-sensitive positions.
These thresholds matter practically. Someone with low-level residual metabolites from a single use two weeks ago might fall below 50 ng/mL and pass the screen, while a heavy daily user could remain above that cutoff for weeks after their last use.
Federal Workplace Testing and Marijuana
Despite shifting state laws and an executive order in December 2025 directing the rescheduling of marijuana from Schedule I to Schedule III, federal drug testing rules have not changed. The Department of Transportation has stated clearly that marijuana remains unacceptable for safety-sensitive employees and that testing protocols, cutoff levels, and consequences stay the same until any rescheduling process is fully complete. Laboratories and medical review officers continue to follow the same regulations. If your job falls under federal testing requirements, a positive test for marijuana is still treated the same way it has been for years, regardless of what your state allows.