How long does weed stay in your system? There's one particular time frame that always gets mentioned: 30 days. Unfortunately it's not that simple. Marijuana can linger in your body for a longer — or shorter — period of time depending on a variety of factors.
This is due to the properties of tetrahydrocannabinol, the primary psychoactive ingredient in cannabis. THC is fat-soluble, not water-soluble, which means it stores longer in the body. If THC were water-soluble, it would dissolve within the body and depart your system within days via urine.
THC's fat-solubility means that body fat percentage plays a huge role in the amount of time weed remains in your body. The amount and frequency you smoke or eat plays a role as well. Exercise patterns and diet also contribute to its storage.
Alan Shackelford, a former clinical and research fellow at Harvard Medical School, drove home this point in the Cannabist. "Unlike alcohol, there is no easy or relatively reliable way to predict how quickly THC will be metabolized or no longer be detectable in blood or urine," he said.
In that case, is there at least a general estimate to predict the amount of time weed stays within the body? This nifty chart from Green Rush Daily could serve as a helpful indicator but, again, it depends on more factors than just body fat and frequency of consumption.
Traces of THC also depend on the method of testing. A marijuana user could potentially pass a urine test after seven days, while hair can retain THC for 90-plus days.
For now, it remains difficult to pinpoint the exact amount of time weed will stay in your system. But with marijuana laws continuing to loosen around the country, perhaps drug tests won't be as necessary going forward.