How Long Does Marijuana Stay in Your System?

If you’ve ever used cannabis, you’ve probably also wondered: how long does marijuana stay in your system? Whether you need to pass an upcoming drug test that screens for marijuana or you’re simply interested as a conscious consumer, the thing you need to know is there is no hard and fast rule for how long marijuana will stay in your system.



However, that doesn’t mean that you can’t make an educated guess! Conventional wisdom has long held that 30 days is the threshold after which your system will be free of marijuana and that’s a decent rule of thumb to follow if the stakes are high and you’re better safe than sorry.

That said, there have been several medical studies that challenge this baseline threshold.

What Science Says

In 2005, Paul Cary of the University of Missouri’s Toxicology and Drug Monitoring Laboratory conducted a review of 8 prior studies that had reported marijuana detected in participants’ systems for over 25 days. The results? The review found that detection times over 30 days can occur but those cases are outliers.

Take one 1989 study included in Cary’s review. It was performed with chronic marijuana users and did show a max detection timeline of 25 days. However, only one test subject was positive for marijuana after 14 days of cessation. Not only that, but the average time before cannabinoids were undetectable was only 9.8 days!

In Cary’s conclusion, he suggests that “it would be unlikely for a chronic user to produce a positive urine drug test result for longer than 10 days after the last smoking episode.” Keep in mind that this study tested participants with kits that had the standard cutoff of 50 ng/mL of cannabinoids. Should the test sensitivity be dropped to 20 ng/mL, the detection window might grow to around 21 days even for heavy users.

Modifying Factors

2970563512_e82586159c_bOf course, there are several factors that can affect how quickly your body metabolizes cannabinoids. For example, how long does marijuana stay in your system if you only smoke occasionally, or have only recently tried it? Well, Cary has an answer for that as well: “It would be unusual for the detection of cannabinoids in urine to extend beyond 3-4 days following the smoking episode”.

Keep these other factors in mind as well:

  • Body Weight: THC, the main psychoactive component of marijuana, stores itself in your fat cells once it leaves the bloodstream. This means that the more body fat you have, the more THC you’ll end up storing.
  • Activity Levels: Exercise is a bit of a double-edged sword here. It turns out that in the short term, exercise increases the concentration of THC in your blood, so don’t go out for a 4k right before a drug test. However, in the long term, regular exercise means that you’re burning more fat cells than a sedentary person, and therefore eliminating marijuana from your system at a faster rate.
  • Metabolism & Health: Your overall metabolism can give you a good idea of whether you’ll metabolize THC faster or slower than others.

The Bottom Line

Unfortunately, the only way to be absolutely sure of how long marijuana stays in your system is to test yourself. One way to do this is to stop consuming cannabis and give yourself tests after one, two, and three weeks. This will give you the clearest picture of how long marijuana stays in your system at your current metabolism and smoking rate.

Article By: Spencer Grey