Factors Affecting How Long THC Stays in Your System

Short answer

Most people who use cannabis once or twice clear THC from urine in 3 to 5 days. Daily users often test positive for 30 days or longer. Blood and saliva clear in hours to a few days. Hair holds THC for up to 90 days. Your own timeline depends on the factors below, and no single product or drink reliably resets it.

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Detection windows by sample type

• Blood: 1 to 2 days after occasional use, up to 7 days after heavy use.
• Saliva: 24 to 72 hours, longer after edibles or concentrates.
• Urine: 3 to 5 days for occasional use, 10 to 30 days for chronic use.
• Hair: up to 90 days, measured from the follicle end outward.

Factors that affect how long THC stays in your system

1. Frequency and duration of use

This is the largest variable. THC and its metabolite THC-COOH build up in fatty tissue with repeated use. Someone who smokes a few times a month starts from a low baseline and clears fast. Someone who uses daily for years carries a large stored load that sheds into the bloodstream for weeks.

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2. Body fat percentage

THC is fat soluble, so it parks in adipose tissue and leaves slowly. Two people with the same habit can show different timelines if one has a higher body fat percentage. Body composition matters more than total body weight here.

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3. Metabolism and liver enzymes

The liver breaks THC down with enzymes in the CYP2C9 and CYP3A4 families. Genetic differences, age, and liver health change how fast that work happens. A faster metabolizer clears metabolites sooner, though stored THC still has to be released first.

4. Dose, potency, and route of administration

A single low-potency joint delivers far less THC than a dab, a vape cartridge, or a 50 mg edible. Edibles pass through the liver and produce more THC-COOH than inhaled flower, which extends urine detection. Higher doses and higher potency products take longer to clear.

5. Hydration, diet, and physical activity

Water supports normal kidney function but does not dissolve stored THC. Heavy exercise can release THC from fat stores, which may raise levels for a short period. Crash dieting and fasting do the same thing by mobilizing fat.

6. Age and overall health

Older adults and people with slower metabolisms tend to clear metabolites at a lower rate. Conditions that affect liver or kidney function shift the timeline as well.

7. The test itself

Cutoff thresholds decide the result. Federal workplace urine testing screens at 50 ng/mL and confirms positives at 15 ng/mL by mass spectrometry. A test with a lower cutoff can flag a sample that a 50 ng/mL screen would pass, and hair or blood tests follow different windows than urine.

What does not work

Detox teas, niacin, vinegar, and herbal cleansers have no evidence behind them. Drinking large volumes of water before a test can dilute a sample enough to trigger a negative-dilute flag, which labs report as an invalid result rather than a pass.

Bottom line

Track how often you use, how potent the product is, and how you consume it. Those three inputs explain most of the difference between a 4-day clearance and a 30-day one.