The short answer

Cannabis does not have a single half-life. THC clears in two phases: an early distribution phase of roughly 1.5 to 4 hours, and a terminal phase of about 20 to 30 hours in heavy, long-term users. THC-COOH, the metabolite most drug tests detect, has a terminal half-life near 3 to 13 days and can run longer with daily high-dose use. The main drivers are route of administration, dose and potency, how often you use, body fat, liver enzyme activity, genetics, age, and other drugs in your system.

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Route of administration

Inhaled THC peaks within minutes and starts clearing right away, so the effective half-life stays short. Oral products absorb over a period of hours, which keeps feeding THC into the blood long after you swallow the dose. That extended absorption stretches the apparent half-life and pushes detection windows out by days compared with flower.

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Frequency and duration of use

Someone who vapes twice a month clears THC from blood in a day or two. A daily user builds a reservoir in fat tissue, and that reservoir trickles THC back into circulation for weeks. Chronic use is the single largest multiplier on terminal half-life.

how long is cannabis half life in your body

Body fat and composition

THC is lipophilic, meaning it binds to fat. A higher fat mass creates a larger storage depot and a slower terminal phase. Lean users with low body fat tend to clear the metabolite faster than users with the same intake and higher fat mass.

THC Half-Life in Urine vs Blood: Detection Windows Compared

Liver enzymes and genetics

Cytochrome P450 enzymes, mainly CYP2C9 and CYP3A4, break THC down. Genetic variants in these enzymes can slow or speed that work by several fold. Liver disease, hepatitis, and heavy alcohol use also reduce clearance and extend the half-life.

Age and sex

Liver enzyme activity and lean body mass decline with age, so older users generally clear cannabinoids at a slower rate. Body composition differences between sexes change distribution volume, which shifts how long THC stays measurable.

Potency and cannabinoid mix

A 30 percent THC concentrate delivers far more drug than a 15 percent flower sample, and higher input means longer time above the detection threshold. CBD and CBN compete for some of the same enzymes, so full-spectrum products can alter how fast THC is processed.

Other drugs and alcohol

Medications that inhibit CYP enzymes, including some antifungals, antibiotics, and antidepressants, can slow THC metabolism and extend its half-life. Alcohol competes for the same liver pathways.

Diet, hydration, and activity

These have a smaller effect than most people assume. Exercise can release stored THC into blood for a short window, which raises measured levels rather than lowering them. Water intake does not speed hepatic clearance in any meaningful way.

How to estimate your own timeline

  1. Record the route, dose, potency, and the exact time of your last use.
  2. Classify your use pattern as occasional, weekly, or daily.
  3. List anything that slows liver enzymes, including prescriptions, alcohol, and liver conditions.
  4. Compare your profile against the published ranges for occasional and chronic users.
  5. Use a lab test if you need a definitive number for a legal, medical, or employment reason.

No formula produces an exact figure. Half-life describes a population average, and individual results vary by a wide margin.

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