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Since I don’t like inhaling things, I’d always avoided marijuana. A few months ago, I discovered weed gummies and I find they help me calm down in the evening so I can sleep. How long should I be waiting to drive after taking them? Even after a year of legalization, I’m really not clear on how marijuana affects driving. – Carin, Vancouver

With pot edibles, figuring out when you’ll be safe to drive is a lot hazier than if you’ve smoked or vaped. But you should be waiting longer than you think.

“Edibles are different from inhaling – they affect every single person differently and each edible has different effects,” says Andrew Murie, CEO of Mothers Against Drink Driving (MADD) Canada. “For edibles, you really need to sleep it off. If you’ve really overdone it, you could still be having some of the effects the next morning.”

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Exactly how long should you be waiting? There’s no clear answer yet. But it should be longer than if you’d inhaled.

On its website, Health Canada says, generally, the effects of inhaled cannabis could last six hours or more. But if you eat or drink it, the effects could last up to 12 hours.

“With edibles, the impairment lasts longer and it takes longer to dissipate from the body,” Murie says.

And the after-effects of both, including drowsiness, could last up to 24 hours.

Ottawa says it won’t give guidelines on how long you should be waiting to drive after eating or inhaling it.

The Centre for Addiction and Mental Health (CAMH) recommends that people wait at least six hours before driving after smoking pot.

“Six hours is a general guideline for inhaling, but it doesn’t apply to medical users, new users or people who are mixing it with alcohol or other drugs, who all have to wait longer,” Murie says. “Edibles are a lot less predictable – nobody’s comfortable putting a number on it.”

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Don’t eat and drive

You’ll feel the effect of vaping or smoking pot within 30 minutes. But with edibles, it can take up to two hours to start to feel the effects and up to four hours to feel the full effects.

“You might eat a cookie and think you’ve got an hour and a half to get home, but what if it kicks while you’re on the road?” Murie says.

He suggests going “low and slow” – consuming a small amount, seeing how it affects you and not driving at all until the next day.

“Do not mix it with alcohol, it makes the impairment worse,” Murie says.

New rules came into effect last week that allow cannabis edibles and oils to be approved by Health Canada and, eventually, sold legally in stores.

Those rules also limit the amount of THC, the psychoactive component of cannabis, to 10 milligrams. But there are edibles already out there, sold on the internet and in dispensaries.

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“Until now, there was no research on edibles and impairment because they were illegal,” Murie says. “We won’t know what a cookie with 2.5 milligrams of THC will have on driving until there’s research.”

Could you be charged?

If you think you’re safe to drive just a couple of hours after a few gummies, you still might be over the legal limit to drive a car.

If police suspect you’re impaired by pot, however you’ve consumed it, they can either ask you to take an oral fluid test – where they take a scrape of saliva off your tongue and put it into a machine – or the standard field sobriety test.

The oral fluid test doesn’t show the specific level of THC in your blood, but it reads fail if you are above 5 milligrams, the minimum amount for a criminal charge.

“I feel really conformable saying that anybody who fails the oral fluid test took cannabis in the last couple of hours and shouldn’t be driving,” Murie says.

You won’t be charged based on the oral fluid test. Instead, if you failed either test, then police could demand a blood test, which would show your actual blood concentration of THC. You’d be charged based on that.

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But by the time you actually get a blood test, you might have no THC in your blood. And, a year into legalization, many police forces have had struggles figuring out how to get blood tests done at all, Murie says,

While the RCMP’s National Forensic Laboratory expected to see 800 blood tests in the first year, there’ve only been about 215, the RCMP says.

“With cannabis, if you wait more than two hours, it might be gone,” Murie says. “And there’s been a big problem so far with the timeliness of these blood tests.”

Editor’s note: A previous version of this article stated that new Health Canada rules limited the amount of THC in cannabis edibles and oil to 10 nanograms. It is in fact 10 milligrams. The Globe regrets the error.

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