There are many things that can affect how long marijuana stays in your system. Some of these factors, like your age, gender, and body mass index (BMI), have less to do with the drug itself and more to do with how your body absorbs and uses it. There are other things that have to do with how you use marijuana. This includes how much you take and for how long (frequency). Higher doses and more frequent use of marijuana seem to make it take longer for it to leave your body. Marijuana with more THC can also stay in your body for a longer time. When you eat marijuana, it stays in your body a little longer than when you smoke it.