Test Details: The principal psychoactive cannabinoid is delta – 9 - tetrahydrocannabinol (THC) which is released slowly from tissue storage sites. Infrequent smokers may test positive for 2 to 5 days after last Marijuana / Hashish use; chronic smokers may test positive even 3 to 4 weeks after abstinence. False positive result may be seen with Ketoconazole. A single urine test cannot differentiate casual use from chronic drug abuse. Urine drug testing cannot predict extent of impairment, drug dose or exact time of use.