How Quickly Does Cannabis Enter Your System, and How Long Does It Stay There?

For all the newcomers to cannabis culture out there, here's everything you wanted to know about how quickly weed takes effect, how long the high will last and how long cannabis can be detected on a drug test.

How quickly does cannabis enter your system?

The answer to that question largely depends upon how you choose to consume cannabis. Dr. Robert Mann - a senior scientist at the University of Toronto's Centre for Addiction and Mental Health - says smoking or vaping cannabis is a "very efficient way to get the drug into your bloodstream." He says that according to his research most people will reach the peak of their high about five minutes after they've smoked a joint.

Things are quite a bit different for marijuana-infused edibles however. If you prefer to eat cannabis-infused snacks as opposed to smoking or vaping you should plan for the effects to start setting in up to two hours after you ate it.

How long will weed stay in your system?

After you hit that peak level of intoxication, it'll take a few hours for the THC—the chemical in marijuana largely responsible for giving you that high—in your body to come back down, according to Dr. Mann.

"THC levels will decline over the next couple of hours very rapidly, then that decline slows off for a while, and then after several hours, I think the levels in the blood are quite low," Mann told Global News.

He suggests that after about six hours you should be ok to drive, though you shouldn't be afraid to wait longer if you don't think the effects have worn off yet. And if you do decide to consume cannabis edibles, waiting for about eight hours or so after you start feeling intoxicated before driving is probably best.

Of course the method of consuming cannabis isn't the only thing that dictates how long your high lasts and how intense it will be, says M-J Milloy - the Canopy Growth professor of cannabis science at the University of British Columbia. How much you take and how strong your cannabis is will play a part in that as well.

"Cannabis' effect on individuals as well as its detectability really varies by what people are using," he said. "And if they are, for example, smoking high-THC joints, that's a different thing than if they are taking gel caps of high-CBD cannabis."

Even simple things like "how deeply you might inhale, how long you hold the inhalation for" contribute to what your cannabis experience will be like says Mann.

How long can cannabis be detected by a drug test?

Because of the way that cannabis interacts with the body you could test positive for the stuff on a drug test long after the last time you consumed. Different studies have detected cannabis in urine samples up to a month after the last time a person consumed marijuana.

"When you use cannabis, the THC gets absorbed into the fat in your body, and so there's kind of a reservoir there that keeps getting released fairly slowly, so that you will find trace amounts of THC in the blood for a longer period of time, but at very low levels," Mann said.

And the more often you consume cannabis, the more likely it is that THC can be detected in your blood or urine for extended periods of time, where as the occasional consumer will flush it out much more quickly.

"If you're a frequent user, there are people who use daily or several times a day, it builds up in your system. It's in your body at higher levels for a longer period of time just because it's building up in the body."

So, if you're hoping to become a pilot or enter some other safety-critical occupation you'll want to make sure you lay off the marijuana at least 30 days before you go for your drug testing.

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