THC half-life is driven mainly by how often you use, how much body fat you carry, your liver enzymes and genetics, the route of administration, and the dose. Plasma THC clears in roughly 1 to 3 days for occasional users and 5 to 13 days for heavy chronic users, while urine detection can run from 3 days to more than a month.
How long does THC stay in the body?
Smoked THC peaks within minutes and falls with a plasma half-life of about 1 to 3 days, but chronic heavy users can show terminal half-lives of 5 to 13 days because fat stores keep leaking small amounts into blood. Urine screens look for THC-COOH, a metabolite, not THC itself, so positives typically last 3 to 7 days after a single use, 10 to 21 days with regular use, and a month or longer with daily heavy use.
What factors change cannabis half-life?
Six variables do most of the work: dose and potency, frequency of use, body composition, liver metabolism and genetics, route of administration, and drug interactions. Everything else, from strain name to water intake, is a minor modifier at best.
How does frequency of use affect half-life?
Daily use loads fat tissue with cannabinoids and stretches the slow release phase, so total clearance takes longer. Occasional users clear THC and its metabolites faster because they carry smaller stored reserves.
How does body fat affect THC half-life?
THC is highly lipophilic and partitions into fat, so a higher body fat percentage means a larger reservoir and a longer terminal half-life. Leaner users often test negative sooner, though enzyme activity still matters more than weight alone.
How do liver enzymes and genetics affect it?
THC is cleared by CYP2C9 and CYP3A4 in the liver, and CYP2C9 poor metabolizers eliminate it more slowly. Age, liver health, and enzyme inhibitors such as CBD or ketoconazole also slow clearance.
Does route of administration matter?
Inhaled THC reaches the bloodstream fast and clears with a short half-life measured in hours to a couple of days. Edibles absorb slowly, pass through the liver into 11-hydroxy-THC, and can keep detectable levels around longer than inhaled flower or vape.
Do other drugs and CBD change THC half-life?
CYP inhibitors such as CBD, ketoconazole, and some antidepressants can slow THC breakdown, while inducers like rifampin speed it up. High-dose CBD taken alongside THC can raise THC blood levels and extend detection windows.
Do sex, age, and activity level matter?
These have small effects next to dose and frequency. Exercise mobilizes stored THC briefly, which can nudge a test result, and older adults often clear drugs more slowly.
What does not change cannabis half-life?
Strain names, indica versus sativa labels, and tolerance do not meaningfully change pharmacokinetics. Potency and dose do, because a larger dose takes more half-lives to fall below a detection threshold.
Why the half-life matters for dosing and drug tests
THC leaves plasma in days but lingers in fat for weeks, so redosing often builds a steady baseline that raises tolerance and extends positives. If you face a urine screen, plan around weeks rather than days, and remember that lab confirmation quantifies THC-COOH better than an at-home strip.