Cannabis can change how anesthesia and recovery work, so your anesthesiologist needs to know about it before surgery. The sources say cannabis use may affect the amount of anesthesia you need, your risk for heart or breathing problems, the pain medicine you may need after surgery, your risk of nausea and vomiting, and the chance of withdrawal symptoms after surgery. Regular users may also have more pain and nausea after surgery and may need more or different pain medicine. Smoking marijuana shortly before surgery can also raise heart rate and blood pressure and may increase the risk of a surgery-related heart attack.

Timing matters. It is not advisable to smoke marijuana on the day of surgery. ASRA Pain Medicine advises waiting at least 2 hours after the last smoke before elective surgery, and the American College of Surgeons says not to use cannabis products within 72 hours of general anesthesia. After surgery, research has not established when it is safe to resume smoking weed.

Some cannabinoid medicines should be continued, not stopped suddenly, including certain FDA-approved products such as dronabinol, nabilone, and Epidiolex. Verify the exact plan with your surgical or anesthesia team in case they want something different for you.