 [ Symptoms ] how long does thc stay in your system [ Disease ] this question does not have a straightforward answer unfortunately the active ingredient in marijuana is called delta 9 tetrahydrocannabinol or thc for short when a person smokes marijuana the thc is rapidly absorbed by the body which causes the person to feel high  this effect is short lived lasting maybe three or four hours however an inactive form of thc called delta thc acid deposits itself in the fatty tissue this is called the metabolite of thc many marijuana tests do not look for active thc in the blood stream or urine instead they look for this thc metabolite despite a common belief that it takes longer for heavy pot users to test clean than someone who smoked marijuana just one time there is not much scientific evidence to support that idea every individual is body is unique some people is bodies may clear the thc metabolite more rapidly than others detecting thc depends on the type of test used also some very sensitive tests can measure delta thc acid levels up to 25 days after the person stopped using marijuana while it would be nice to have a solid answer to the question of how long thc stays in your system after smoking marijuana it is just not possible to say with certainty