Why Marijuana is detectable a long time after use?

Marijuana and its active ingredient THC is tested for in most drug tests. After one-off or occasional use its break-down products or metabolites can be detected between 3-5 days after use.

However, Marijuana's THC can be detected in a chronic user up to 12 weeks after use although the average is 25-27 days.

Marijuana is highly detectable a long time after use because THC lingers in the fatty tissues of the body and leaks steadily into the blood and then the urine over weeks.

False positives have been known to be triggered by consuming hemp-seed bars and other products, although the more detailed, more expensive gas chromatograph-mass spectrometer (GCMS) test can tell the difference.