How long does cannabis stay in your system?

While the effects of cannabis may wear off in a few hours, depending on the method of consumption, cannabinoids like THC—the intoxicating compound in cannabis—may be detectable for weeks after the high has faded away.

There are numerous factors in determining how long it will take for an individual to metabolize THC, explains Avery Sapoznikow, a researcher at the University of British Columbia’s Therapeutic, Recreational and Problematic Substance Use Lab and an executive board member with Canadian Students for Sensible Drug Policy.

“Frequency of use is probably the most important or impactful,” Sapoznikow suggests. In the casual user—for example, an individual who uses cannabis less than two or three times a month—the body can “break down the THC far faster than in the chronic user,” that is, daily use or at least multiple times weekly, he notes. “In chronic users, THC builds up in the body in the fat stores, which are more difficult to break down.”

 

Does strong weed influence detectability?

The potency of the cannabis consumed can also be a factor in determining how long it remains traceable in the body; the stronger the weed, the more time it takes to break down the biological evidence. Cannabis with high levels of THC will stick around far longer than cannabis containing lower concentrations of the compound. While occasional users may not notice a big difference, sustained, regular use of potent cannabis will build up more quickly and take longer to break down.

Frequency of use is probably the most important or impactful.

“When THC content is higher, there’s more THC that is sent into the bloodstream at a time, which the body will need to process and break down before excretion,” explains Sapoznikow, who points out the rate at which THC is metabolized is also “highly dependent on the route of administration.”

Smoking cannabis results in “an almost instant transmission of THC to the bloodstream,” he notes, but “edible cannabis takes longer to metabolize than smoking. Vaping cannabis is a method that works similarly to smoking… it is also faster to leave the system.”

Study results detailed in Medical News Today note that, in the case of individuals who consume cannabis rarely, cannabinoids are detectable in the system for about three days. In individuals who consume three to four times per week, the window for detection is closer to a week. Daily cannabis users may find that cannabinoids are detectable in their systems for 30 days or more. One older, but oft-cited study of chronic smokers, found that the period could last even longer.

In urine, following smoking, a review of (relatively small) studies indicates that the time period for cannabinoids to be undetectable in the system is about one to three weeks.

Can the type of cannabis testing have any bearing?

The timing and type of test administered can have a significant impact on a user’s results. Blood tests can detect THC for a mere three to four hours, saliva tests can detect cannabis for at least 13.5 hours, although one study reported some participants’ saliva testing positive for THC after as long as eight days and urine tests can detect cannabis for roughly three to 30 days post-use, but there is a chance it could be months.

Clearly, the last represents a big range, but that’s because it all depends on frequency of use, potency of cannabis, body fat and other factors. For example, a first-time user with a low BMI (body mass index) could have a negative test in about three days, whereas a chronic user with a high level of body fat could take months to test cannabinoid-free.

The aforementioned are the most common methods of testing for cannabinoids. Hair tests are more sensitive, though, and Sapoznikow calls them “an entirely different story.”

Cannabis with high levels of THC will stick around far longer than cannabis containing lower concentrations of the compound.

Referring to hair as being akin to “a roadmap to what has been ingested” by the user, Sapoznikow says that THC can be detected in a user’s strands for months after he or she has partaken in a little green. “If someone has long hair and smoked consistently for the duration it was growing, that hair will likely test positive for THC metabolites,” he notes.

Tough to pinpoint how long to metabolize cannabis

Due to the sheer number of variables that determine how a user breaks down cannabinoids, there is no accurate way of pinpointing exactly how long it will take a person to metabolize cannabis. For most users, however, THC should be difficult to trace within a three- to 10-day window, whereas frequent users can expect to wait at least 30 days for similar results—if not longer.

And while cannabinoid and ingredient-du-jour CBD may be metabolized in a similar manner to THC, researchers aren’t sure. “In terms of the length of time CBD stays in the system, there has not been enough rigorous research into this for me to give any sort of timeline for CBD confidently,” says Sapoznikow. “I hope, with legalization opening so many doors for research, that we will soon elucidate the nature of CBD’s metabolization and the length it remains detectable in the human body,” he adds.