Urine drug testing remains the most common method for cannabis screening in employment, legal, and clinical settings. The test detects THC-COOH, a non-psychoactive metabolite store
Urine tests detect THC-COOH (11-nor-9-carboxy-THC), the primary metabolite produced when the liver breaks down THC. Unlike blood or saliva tests that detect active THC, urine tests reveal only past use — not current impairment. Most programmes use a two-step process: an immunoassay screening followed by confirmatory GC/MS testing. Understanding the endocannabinoid system explains why THC metabolites persist in fat-soluble form. Frequent users of high-THC strains like OG Kush may test positive significantly longer due to the lipophilic nature of cannabinoids.
Detection windows vary dramatically depending on frequency of use, body fat percentage, metabolism rate, and potency consumed. Occasional users (1–3 times per week) typically clear within 3–7 days. Moderate users may test positive for 7–21 days. Daily heavy users can remain positive for 30–90 days. Body fat plays a major role since THC-COOH is stored in fat tissue. The standard federal cutoff is 50 ng/mL for immunoassay and 15 ng/mL for GC/MS confirmation. Learn more about how body fat affects THC detection windows specifically.
Multiple physiological factors influence how quickly cannabis clears from urine. Metabolism speed (BMR) is one of the most significant — individuals with faster metabolisms clear THC-COOH more rapidly. The THC content of cannabis consumed matters: high-potency concentrates produce more metabolites than flower. Delta-8 THC produces similar metabolites to delta-9 and will likely trigger a positive result. Hydration affects concentration: dilute urine samples may be flagged as adulterated.
Initial immunoassay screens have a false-positive rate of 5–10%, triggered by ibuprofen, proton pump inhibitors, CBD products with trace THC, and certain antibiotics. If you test positive on a screening, request GC/MS confirmation immediately. GC/MS is the definitive gold standard with virtually zero false positives. See the full breakdown of false positive causes in drug testing before accepting any result. Medical Review Officers evaluate positive results in workplace contexts. Understand how THC differs from CBD in terms of what tests detect.