Quick answer to how long marijuana stays in your system: 7-31 days depending upon usage and potency.
The drug marijuana enters the body through oral consumption (eating) or the more common method of smoke inhalation. Depending upon the potency of the marijuana varying levels of tetrahydrocannabinol, or THC, the psychoactive chemical in marijuana, will remain in the blood stream and urine. On average, trace amounts of THC can be detected up to 4 weeks after use. For light users smoking less potent marijuana, the THC will be expelled from the body’s system in as little as 3 or 4 days. How long THC can be detected in moderate users is an average range of 1-2 weeks while heavy, everyday users can have traces of marijuana detected in their urine up to 31 days after initial use has ceased.
The question of how long marijuana stays in the system is also dependent on which drug testing option is being used. Urine test kits can distinguish THC and marijuana in the body for the previously mentioned lengths of time while hair follicle drug tests can confirm marijuana use months after the last ingestion. Marijuana is stored in the body’s fat cells, which are also present in the bloodstream. This results in blood testing being the most accurate (and the most expensive drug test) and can detect THC use up to 1 year after initial consumption.