how many mg of thc to test positive
Cannabis drug testing The main metabolite excreted in the urine is 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid (delta9-THC-COOH). Most THC drug tests yields a positive result when the concentration of marijuana in urine exceeds 50Â ng/mL.[citation needed] Urine Testing is an immunoassay based test on the principle of competitive binding. Drugs which may be present in the urine specimen compete against their respective drug conjugate for binding sites on their specific antibody. During testing, a urine specimen migrates upward by capillary action. A drug, if present in the urine specimen below its cut-off concentration, will not saturate the binding sites of its specific antibody. The antibody will then react with the drug-protein conjugate and a visible colored line will show up in the test line region of the specific drug strip.[citation needed]