THC can stay in your system anywhere from 24 hours to two months, depending on how often you use cannabis and which type of drug test is involved. A single use might clear in a few days, while daily heavy use can leave detectable traces for weeks. The wide range comes down to how your body stores and processes THC, and how sensitive the test is.
Why THC Lingers Longer Than Other Substances
Most drugs dissolve in water, get processed by your liver and kidneys, and leave your body relatively quickly. THC works differently. It binds to fat molecules, which means your body stores it in fatty tissue rather than flushing it out right away. Over time, those stored metabolites slowly release back into your bloodstream and eventually leave through your urine.
The breakdown product that drug tests actually look for has a half-life of roughly 30 hours in occasional users, meaning it takes about that long for half the amount to leave your body. But with extended monitoring, researchers at Johns Hopkins found that half-life can stretch to 44 to 60 hours. That slow, steady release from fat tissue is the reason cannabis has one of the longest detection windows of any commonly tested substance.
Detection Windows by Test Type
Urine Tests
Urine testing is the most common method for workplace and legal drug screening. How long THC metabolites show up depends heavily on your usage pattern:
- Moderate use (a few times per week): up to 5 days
- Heavy use (daily or near-daily): up to 10 days
- Heavy chronic use (multiple times daily over months): up to 2 months
These timelines assume the standard screening cutoff of 50 nanograms per milliliter (ng/mL), which is the threshold set by federal regulations for most workplace testing programs. Some tests use a more sensitive cutoff of 15 ng/mL, which can extend the detection window by several days or more. If a test comes back positive at the initial 50 ng/mL screen, a confirmatory test at the 15 ng/mL level is typically run to verify the result.
Saliva Tests
Oral fluid tests detect THC itself, not its metabolites, which makes for a much shorter window. Cannabis is generally detectable in saliva for up to 24 hours after use. This makes saliva tests better suited for detecting very recent use, like roadside testing after a traffic stop, rather than patterns of use over time.
Blood Tests
Blood tests also detect active THC rather than stored metabolites. THC levels in blood spike quickly after smoking or vaping, then drop sharply within a few hours. For occasional users, blood tests typically come back clean within one to two days. Frequent users may test positive for a few days longer because of the slow release of THC from fat stores back into the bloodstream.
Hair Tests
Hair follicle tests have the longest detection window of any method. As THC metabolites circulate in your blood, small amounts get deposited into growing hair. A standard hair test analyzes 1.5 inches of growth closest to the scalp, which represents roughly 90 days of history. Hair tests are less common due to cost and are more often used in legal or forensic settings.
Factors That Change Your Timeline
Body Fat Percentage
Because THC binds to fat, people with a higher body fat percentage have more “storage space” for THC metabolites. Someone with a lower body fat percentage and a faster metabolic rate will generally clear those metabolites more quickly than someone with a higher BMI. This is one of the biggest individual variables and helps explain why two people who use the same amount can test differently weeks later.
How You Consume Cannabis
Smoking or vaping delivers THC to your bloodstream through your lungs almost immediately, creating a sharp peak that drops off relatively fast. Edibles take a different route: THC gets absorbed through your digestive tract and processed by your liver before reaching your bloodstream. This slower absorption means THC enters your system more gradually, the high lasts longer, and the metabolites can take longer to fully clear. Edible use may extend urine detection by several additional days compared to smoking the same amount.
Frequency and Dose
This is the single biggest factor. A person who uses cannabis once builds up a small amount of THC in fat tissue that clears in days. Someone who uses daily for months saturates their fat stores with metabolites, and it can take weeks of abstinence for levels to drop below the testing threshold. The relationship is not linear either. Going from occasional to moderate use might only add a couple of days, but going from moderate to heavy chronic use can add weeks.
Hydration and Exercise
Staying well hydrated keeps your kidneys working efficiently, which helps metabolites leave through urine at a normal rate. Severe dehydration can concentrate your urine and potentially make a borderline result tip positive. Exercise is more complicated. Physical activity burns fat, which releases stored THC metabolites back into your bloodstream. Over time this speeds up clearance, but exercising right before a test could temporarily raise metabolite levels in your urine.
What the Numbers Mean on a Test
Drug tests don’t measure whether you’re currently impaired. They measure whether the concentration of THC metabolites in your sample exceeds a set cutoff. The federal standard for urine screening is 50 ng/mL for the initial test and 15 ng/mL for confirmation. Anything below the cutoff is reported as negative, even if trace amounts are technically present.
This matters because the detection window you’ll find quoted anywhere, including the timelines above, is really the window for staying above that cutoff. A lower cutoff means a longer detection window. If you’re facing a test with a 15 ng/mL threshold rather than 50, you should expect to need more time to test clean, potentially a week or more beyond what the standard timelines suggest.
Home test strips are available at both cutoff levels, so if you want to gauge where you stand before an official screening, match the sensitivity of your home test to whatever standard your employer or testing program uses.