Answer by Nolz Deja. Confidence votes 821. THC is non-existent in urine, when screening for urine it is only the metabolites and byproducts of the drug that are tested for. For a frequent user, the substance may stay in the system up to 40 days after abstaining from use of cannabis or cannabis containing substances.uch longer than any other drug that I know of. Most other drugs are out of your system in a matter of days, or maybe a week â¦ for extremely heavy, long-term users. For regular smokers (people who smoke on a daily basis), marijuana takes anywhere from 2 to 6 weeks to leave your system. So, around a month is a safe bet.