Reviewed and updated: August 2026
Do not drive after using cannabis. THC can impair coordination, reaction time, attention, judgment and distance perception. Combining cannabis with alcohol greatly increases impairment. Cannabis may also interact with prescription, over-the-counter and natural health products, so people taking medication should consult a healthcare professional.
How does cannabis affect driving?
Cannabis can slow reaction time, reduce attention, impair coordination and affect decisions and distance judgment. These are core driving skills. Feeling confident or “used to cannabis” does not prove that driving ability is normal.
Drug-impaired driving is a criminal offence in Canada. Plan a sober ride before consuming and never ride with an impaired driver.
How long should someone wait before driving?
There is no universal time that guarantees safety. Some guidance recommends waiting at least six hours, but Health Canada warns that impairment can last more than 24 hours and depends on dose, potency, route, tolerance and individual factors. Edibles can create especially long and delayed effects.
What happens when cannabis and alcohol are combined?
The combination increases impairment and the risk of injury or death from accidents. It may also intensify dizziness, nausea, poor judgment and loss of coordination. Avoid combining them.
Can cannabis interact with medications?
Yes. THC and CBD can affect drug-metabolizing enzymes and may change the effects or levels of some medicines. Combining cannabis with sedating substances—such as opioids or benzodiazepines—can increase sedation and impairment. Interactions may also matter with antidepressants, anti-seizure medicines, anticoagulants and other drugs.
Do not stop or change a prescription on the basis of an online article. Ask a doctor or pharmacist to review the exact cannabis product, THC/CBD dose and complete medication list.
Safer planning checklist
- Arrange transportation before using cannabis.
- Do not combine cannabis with alcohol.
- Ask a pharmacist about prescriptions, non-prescription drugs and supplements.
- Avoid driving the next morning if effects or drowsiness remain.
- Remember that CBD products may contain THC.
- Call 911 for loss of consciousness, trouble breathing, chest pain or another emergency.
Primary sources: Health Canada, “Cannabis impairment and safety risk”; Health Canada, cannabis information for healthcare professionals; Health Canada consumer guidance.
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