Quick answer
THC has a plasma half-life of about 1.5 to 4 hours. The metabolites it leaves behind do not clear at that pace. The active metabolite 11-OH-THC falls in a similar range. The inactive metabolite THC-COOH has a terminal half-life of 3 to 13 days. In daily users, THC-COOH can stay above urine test cutoffs for up to 30 days.
how long do thc metabolites stay in urine
Half-life tells you how fast a concentration drops by half. It does not tell you when a drug test turns negative. Those are two different questions with two different answers.
cannabis metabolites vs thc what is the difference
What half-life actually measures
Most cannabis half-life figures online mix up two numbers. The distribution half-life (alpha) covers the first hours, when THC moves out of blood and into fat, liver, and other tissue. That phase is short, often under 30 minutes to a couple of hours.
Cannabis Metabolite Testing for Employment: What You Need to Know
The terminal elimination half-life (beta) covers the much slower tail, when the body clears what is left. For THC, that tail runs hours to a few days. For THC-COOH, it runs days. When someone says the half-life of cannabis is 3 to 13 days, they mean THC-COOH, not THC.
The three molecules that matter
THC (delta-9-tetrahydrocannabinol)
The parent compound. It produces the high. Plasma half-life is about 1.5 to 4 hours after smoking. Edibles stretch absorption over a longer window, so peak levels arrive later and decline over more hours.
11-OH-THC (11-hydroxy-THC)
The liver converts THC into this metabolite through CYP2C9 and CYP3A4. 11-OH-THC is psychoactive, and some research suggests it is more potent than THC itself. Its half-life is close to THC, in the range of a few hours. Edibles produce higher 11-OH-THC levels than smoking because more THC passes through the liver on the first pass.
THC-COOH (11-nor-9-carboxy-THC)
The final inactive metabolite. It is not psychoactive and it is the molecule most drug tests target. THC-COOH has a terminal half-life of 3 to 13 days. It binds to fat tissue, then leaches back into the bloodstream for slow removal through urine and bile.
Half-life numbers at a glance
- THC plasma half-life: about 1.5 to 4 hours
- 11-OH-THC half-life: about 2 to 5 hours
- THC-COOH terminal half-life: 3 to 13 days
- Single-use urine detection: 3 to 5 days
- Daily chronic use urine detection: up to 30 days
- Blood detection: 1 to 2 days for casual use, longer with heavy use
Why THC-COOH outlasts everything else
THC is fat soluble, and THC-COOH distributes into fatty tissue in a similar way. After you use cannabis, both compounds settle into adipose tissue, the liver, and other organs. Blood levels drop fast because the drug leaves circulation. It does not leave the body. It leaves the blood.
From that stored pool, THC-COOH re-enters circulation at a slow rate. That constant trickle is what stretches the terminal half-life into days. A person with more body fat tends to release the metabolite over a longer period than a lean person with the same intake.
What shifts your personal timeline
Half-life values come from averages. Your numbers can land at either end of the range.
- Use frequency and dose: daily high-dose use builds a larger stored pool than a single session.
- Body fat percentage: more fat means more storage and slower release.
- Liver enzymes: CYP2C9 and CYP3A4 activity varies between people and changes with other drugs.
- Route of use: edibles convert more THC to 11-OH-THC and can extend total exposure.
- Age and liver or kidney health: clearance slows with each.
- Hydration: does not flush THC-COOH out on command, but it affects urine concentration and test sensitivity.
How to estimate your own window
- Write down the date and time of your last use.
- Classify your pattern as one-time, occasional (a few times per month), or daily.
- Pick a terminal half-life for that pattern. One-time use sits near the low end, around 3 days. Daily use sits near the high end, closer to 13 days.
- Multiply by five. That is the point where about 97 percent of the metabolite has cleared in a typical person.
- Add a buffer of several days if you carry more body fat or use high-dose edibles.
- Treat the result as a range, not a fixed date. Individual results vary.
Bottom line
THC clears fast. THC-COOH does not. If you are trying to understand a detection window, look at the metabolite half-life, not the THC half-life. For occasional users that usually means days. For daily users it can mean weeks.