How long do drug tests detect marijuana? There is no simple answer to this question. Detection time depends strongly on the kind and sensitivity of the test employed; the frequency, dosage, and last time of use; the individual subject’s genetic makeup, the state of one’s metabolism, digestive and excretory systems; and other random, unknown factors.

The basic drug test types and their approximate detection times are shown in the table below.

Urine Blood Hair Saliva
Marijuana – Single Use 1-7+ days 12-24 hrs Doubtful Not validated
(0 -24 hours?)
Marijuana – Regular Use 7-100 days 2-7 days Months

The most popular kind of drug test is the urine test, which can detect marijuana for days or weeks after use. Note that urine tests do not detect the psychoactive component in marijuana, THC (delta-9-tetrahydrocannabinol), and therefore in no way measure impairment; rather, they detect the non-psychoactive marijuana metabolite THC-COOH, which can linger in the body for days and weeks with no impairing effects. Because of THC-COOH’s unusually long elimination time, urine tests are more sensitive to marijuana than other commonly used drugs. According to a survey by Quest Diagnostics, 50% of all drug test positives are for marijuana.