Cannabis (Marijuana) Use & Surgery: What You Need to Know
Using cannabis (marijuana) can affect your body during and after surgery. Cutting back or stopping cannabis use before surgery can:
Make your breathing and lung health better
Lower stress on your heart
Reduce the amount of pain medication you need
Decrease nausea and vomiting
Prevent reactions to anesthesia (the medicine that puts you to sleep during surgery)
Why We Ask About Cannabis Use Before Surgery?
Cannabis can change how your body reacts to anesthesia and pain medicine. We share this information with everyone who uses cannabis so you can prepare safely and have the best possible recovery.
What Can You Do Before Surgery?
If you use cannabis under the supervision of a medical provider, speak with them about whether you should decrease or stop your use before surgery.
If you use cannabis occasionally (less than 4 days per week)
Stop using it at least 72 hours (3 days) before surgery.
This includes smoking, vaping, edibles, and oils - but not topical creams.
If you are intoxicated (high) on the day of surgery, your surgery will be delayed or cancelled unless it is an emergency.
Being high can seriously affect how your body responds to surgery and may even put your life at risk.
If you use cannabis daily or in large amounts
You are considered a heavy user if you:
Smoke or vape more than 1.5 grams per day
Use more than 300 mg per day of CBD (oil, edibles, etc.)
Use more than 20 mg per day of THC (oil, edibles, etc.)
Use cannabis 2 or more times per day, or use unknown or high-dose products regularly
If this applies to you:
Stopping suddenly can cause unpleasant withdrawal symptoms (cannabis withdrawal syndrome).
Try to slowly reduce the amount you use each day over 7 days, then stop at least 72 hours before surgery.
Cannabis Withdrawal Syndrome (CWS)
Withdrawal from cannabis is not dangerous, but quitting suddenly can make you uncomfortable.
Symptoms may include:
Trouble sleeping
Anxiety or irritability
Headaches or stomach upset
These usually begin 1-2 days after stopping and may last up to 3 weeks. Cutting back slowly can reduce or prevent these symptoms.
Follow Canada's Lower Risk Cannabis Use Guidelines
Use less often - fewer days per week means fewer health risks
Choose products with more CBD and less THC - high THC levels increase the chance of side effects like anxiety and memory problems
Avoid smoking cannabis to protect your lungs from damage and decrease your risk of complications after surgery
Avoid mixing cannabis with alcohol or other substances to reduce your risk of accidents and health problems
Avoid synthetic cannabis products - these can be unpredictable and dangerous
Buy from a licensed cannabis store - that way, you know exactly what is in your product (THC/CBD levels, additives) and avoid harmful contaminants
How to Get Help Before Surgery
If you are ready to reduce or quit cannabis:
Talk to your family doctor or nurse practitioner
Call *811 to speak to a health navigator
Ask your health care team to refer you to an Addiction Medicine specialist
Some people may also meet with an anesthesiologist before surgery to plan pain management and anesthesia safely