 [ Symptoms ] marijuana i have smoked marijuana for about 1 12 months i weigh 130 i have around 1 body fat and my metabolism is very fast and i drink lots of water how long will it take to leave my system [ Disease ] depends on how you are tested hair testing can detect cannabis use for months urine tests for 3 4 weeks the sensitivity of the lab doing the testing is also a factor some labs are more skilled at detecting past drug use