One day in 2016, Jennie awoke to sharp pain and a tugging sensation on the left side of her jaw — "like my jaw was being pulled off my head," she recalls — along with the firm pressure of hands holding her mouth agape. She opened her eyes just enough to see human silhouettes hovering over her. Her body felt heavy, but also like it was floating; she tried to lift her arms, but all she could do was wriggle. What was going on? she wondered, scared.

“She’s waking up,” a male voice said. It was around then that Jennie remembered: She was in the dentist’s office, getting her wisdom teeth pulled. She must have awoken during the procedure. Almost as soon as she realized what was happening, the anesthesia pulled her back into sleep.

Jennie had been smoking weed at least once a day for the past four years. She smoked with her fiancé the day of her wisdom tooth extraction. “I had no idea it was going to affect the anesthesia,” says the 35-year-old, who lives in Arizona. (She requested that Mic publish only her first name out of concern for the legal repercussions of her weed use, since Arizona prohibits recreational cannabis.) Indeed, as legalization sweeps across the country, evidence has emerged that regular marijuana users need more anesthesia for surgery than non-users to ensure they become, and stay, sedated and don't awaken mid-procedure. In plain, very urgent, English: If you consume cannabis on the reg, you need to let your doctor know before you go under for surgery.

Along with anecdotal reports, a 2019 study found that patients who reported smoking weed or ingesting edibles on a daily or weekly basis needed more than double the amount of the anesthetic propofol for endoscopic procedures (like colonoscopies) than non-users. They also needed 19.6% more midazolam and 14% more fentanyl.

Why marijuana increases your need for anesthesia remains unclear, largely because of its status as a federally illegal drug, which makes it difficult to research, Jeffrey Uppington, an anesthesiologist at UC Davis Medical Center, tells Mic. It’s possible that compounds in weed called cannabinoids — which tetrahydrocannabinol (THC, which is responsible for making you feel high) — affect the same receptors in the brain and spinal cord as anesthesia drugs do.

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But, “that’s more speculation than we really know,” Uppington says. “The bottom line is, if you’re a chronic user of marijuana, you are more resistant to anesthetics, both those that put you to sleep, like propofol, and those that keep you asleep, like various anesthesia gases.”

Thanks to modern-day monitors that measure brain waves and other vitals, an anesthesiologist can likely spot when a patient is about to awaken and give them more drugs before they reach that point, Uppington says. But even if you don’t wake up during a procedure, you can still have issues. If you routinely smoke weed, your airway might be more reactive during anesthesia. You might cough more, experience bronchial spasms, and/or have a more active gag reflex, which is a problem if you need to be intubated, as with general anesthesia (the kind that puts you to sleep).

"If you’re a chronic user of marijuana, you are more resistant to anesthetics, both those that put you to sleep, like propofol, and those that keep you asleep, like various anesthesia gases."

After surgery, you might also experience more pain, which may nudge you toward using more opioids and increase your risk of addiction to these substances, says David Hepner, the medical director of the Weiner Center for Preoperative Evaluation at Brigham and Women's Hospital and an associate professor of anaesthesia at Harvard Medical School.

High doses of anesthesia also carry risks, such as causing significant drops in blood pressure, which may lead to a heart attack in at-risk patients, They may also delay awakening, Hepner tells Mic. For instance, propofol usually wears off in about five to 10 minutes but a marijuana user who requires a higher dose may take longer to awaken, delaying them from resuming their normal, day-to-day life.

Jennie’s wisdom tooth extraction left her so groggy that she needed to be transported to her car by wheelchair, and she doesn’t remember anything from the 45-minute ride home. As her fiancé drove, she drifted in and out of sleep, and didn’t feel like herself again for another three hours. In contrast, a friend she drove home after a dental procedure was a little groggy, but could walk to his car and felt fine when he got home, probably because he wasn't a cannabis user, and therefore didn't require as much anesthesia.

The amount of cannabis you need to consume for it increase your resistance to anesthesia remains unclear, though. Determining this threshold is tricky, thanks to the varying concentrations of THC from one product to the next, how long you hold the smoke in your lungs, and the many other variables involved, Uppington says. But it’s probably safe to say that using cannabis every day for a few years is more likely to affect your response to anesthesia than using it just once.

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If you do smoke cannabis regularly, tell your anesthesiologist how much and how often, as well as the last time you smoked, Uppington says. They can then assess whether your use could increase your risk of being resistant to anesthesia and make adjustments accordingly.

While disclosing your weed use may feel embarrassing or even dangerous, remember that your doctor’s job isn’t to judge you, Hepner says. “We just want to understand the health of the patient and how the body may react to different medications to give them the most pain-free procedure.” He adds that it’s also important to mention any other substances or medications you’re taking, since they, too, may react with the anesthesia. Since physicians take an oath to protect patient confidentiality, they wouldn’t disclose your use of cannabis or other substances to your family, law enforcement, or anyone other than the medical professionals directly involved in your care.

No matter how often you consume cannabis, though, don’t use it at all on the day of your procedure, Hepner says. Taking an edible on the same day poses the added risk of inhaling it, which may result in a life-threatening lung infection called aspiration pneumonia. And if you come into the clinic high AF, you can pretty much count on your surgery being cancelled. Uppington recommends hitting pause for as many days as you can before your surgery, ideally a month, which is how long it takes for cannabis to be fully removed from the body.

Awakening mid-wisdom tooth extraction was eye-opening for Jennie. Since her doctor didn’t ask her specifically about her drug use, and she didn’t think smoking weed wouldn't matter for her surgery, she didn’t mention it; in fact, she worried that if she did, she wouldn’t be allowed to undergo the procedure. “In the future, I would definitely inform my doctor of my cannabis use,” she says.