Cannabis and anesthesia: what you should tell us

Not a legal question — a dosing one. Cannabis users need measurably more propofol, and the airway and pain effects are worth knowing before the day.

Reviewed and updated August 2026 · Written by Anastasia Jackson, DNAP, CRNA

Every clinical claim on this page is cited to its source below. How we source clinical content — including the corrections we have made and why.

Anesthesia providers are not asking about cannabis in order to report anyone. They are asking because it changes the dose, and because the consequences of not knowing are real.

The guideline

ASRA Pain Medicine published the first US guidelines on perioperative cannabis in January 2023 — 21 recommendations across preoperative, intraoperative and postoperative care, developed by a 13-member panel including anesthesiologists, chronic pain physicians and a patient advocate, using a modified Delphi method requiring more than 75% agreement. All 21 recommendations achieved full consensus.^1,2

The dose effect, quantified

This is the most consistently reported finding, and it now has numbers behind it.

A separate pooled analysis reported a mean increase of 23.9 mg by fixed-effects model and 36.1 mg by random-effects model.⁶ Requirements for inhalational agents are also increased in retrospective studies,⁷ and a prospective study found cannabis users required significantly higher doses of fentanyl and midazolam as well as propofol.⁷

Clinical studies and case reports have consistently shown increased requirements for GABAergic anesthetic drugs specifically — isoflurane, sevoflurane, propofol, midazolam.⁸ A randomized single-blind study found chronic users required higher propofol doses to achieve loss of consciousness, adequate jaw relaxation and depression of airway reflexes for laryngeal mask insertion.⁹

The other effects worth knowing

Airway

Inhalational use is associated with airway hyperreactivity, increasing the risk of bronchospasm and, in severe cases, life-threatening laryngospasm.⁴ This is a smoke-related effect and does not apply equally to edibles or tinctures — which is why the route of use, not just the fact of use, belongs in the history.

Cardiovascular

Acute intoxication produces tachycardia and hypertension, increasing myocardial oxygen demand and, in the ASRA framing, the risk of myocardial infarction.³ THC may increase catecholamine levels and various cardiac electrical effects have been described, including atrial fibrillation.¹¹ Acute intoxication may also cause lethargy, ataxia, hyperkinesis and tachypnea.⁴

Pain afterward

Counterintuitively for a substance many patients use for pain: regular cannabis use may worsen postoperative pain and increase opioid requirements. In one prospective study, cannabis users reported worse pain and greater functional impairment on the day of surgery and at three and six months afterward compared with non-users.⁴

Synthetic cannabinoids are a different problem

What to disclose, and why it is safe to

Medical cannabis is authorized in 40 states plus the District of Columbia and several territories, and recreational adult use is legal in 24 states and DC.⁷ More than a quarter of Canadian adults report use in the past year.¹² This is a mainstream exposure, and the anesthesia interview is a clinical conversation rather than a legal one.

The specific things worth telling your anesthesia provider:

• Route — smoked, vaped, edible, tincture, topical. Airway effects follow the smoke.
• Frequency — daily use predicts a different dose requirement than occasional use.
• Timing of the last use — the guideline explicitly ties dose adjustment to this.⁵
• What it is for — chronic pain use changes the postoperative analgesic plan.
• CBD products too, including over-the-counter ones, since they are frequently not thought of as drugs.

Frequently asked questions

Should I tell my anesthesiologist I use cannabis?

Yes. ASRA guidelines recommend that all patients undergoing procedures requiring anesthesia be asked about cannabis use, whether medicinal or recreational.² It changes the anesthetic dose and the postoperative pain plan. The interview is clinical, not legal, and universal toxicology testing is specifically not recommended — the point is the conversation.³

Does cannabis affect how much anesthesia I need?

Yes, upward. A meta-analysis of 8 studies with 2,268 patients found cannabis users required an average of 47.3 mg more propofol for induction, with a larger difference for endoscopic sedation (+53.0 mg) than for general anesthesia (+30.6 mg).⁶ Increased requirements have also been reported for inhalational agents, fentanyl and midazolam.⁷

Will my surgery be cancelled if I have used cannabis?

Not for use in general, but yes for acute intoxication. ASRA recommends that elective surgery be postponed or cancelled where there is evidence of acute intoxication such as altered mental status or impaired decision-making capacity⁴ — in part because intoxication can impair the ability to give informed consent.

How long before surgery should I stop using cannabis?

No specific interval has been established in the guidelines, and the effect of perioperative tapering has not been determined.¹⁰ What the guidance does say is that dose adjustment should consider the timing of last consumption,⁵ and that acute intoxication on the day is a reason to postpone. Discuss timing with your anesthesia team rather than guessing.

Do edibles affect anesthesia differently from smoking?

The airway effects differ. Inhalational use is associated with airway hyperreactivity and a higher risk of bronchospasm and laryngospasm;⁴ that risk follows the smoke rather than the THC. Systemic effects on anesthetic requirement are not route-specific in the same way. Tell your provider which route you use.

Does cannabis help with pain after surgery?

The evidence points the other way. Regular use may worsen postoperative pain and increase opioid requirements, and in one prospective study cannabis users reported worse pain and greater functional impairment on the day of surgery and at three and six months afterward.⁴

References

1. Shah S, Schwenk ES, Sondekoppam RV, et al. ASRA Pain Medicine consensus guidelines on the management of the perioperative patient on cannabis and cannabinoids. Reg Anesth Pain Med. 2023;48(3):97–117. doi:10.1136/rapm-2022-104013. PMID 36596580.
2. All patients should be screened for cannabis use before surgery, first US guidelines recommend. ASRA Pain Medicine, 3 January 2023. Describes the 13-expert panel, modified Delphi with >75% agreement, 21 recommendations, all achieving full consensus.
3. ASRA guidelines recommend screening patients for cannabis use before surgery. Summary of the 2023 guideline, including the recommendation against universal toxicology screening and in favor of the Cannabis Use Disorder Identification Test.
4. Perioperative care considerations for patients with cannabis use. Clinician brief summarizing ASRA recommendations, acute intoxication features, airway hyperreactivity, and the prospective study of postoperative pain outcomes.
5. ASRA guidelines for the perioperative patient on cannabis and cannabinoids — guideline summary. Includes the Grade C dose-adjustment recommendation, the EEG monitoring statement, and the pregnancy recommendations.
6. Baker A, Binda DD, et al. Quantitative analysis of propofol dosage in cannabis users: a systematic review and meta-analysis. J Clin Med. 2025. PMC11818839. Eight studies, 2,268 patients; +47.33 mg overall, +30.57 mg for general anesthesia, +53.02 mg for endoscopic sedation.
7. Cannabis and anesthesia: a 2025 update on perioperative considerations. APSF Newsletter, Anesthesia Patient Safety Foundation. Summarizes two meta-analyses (2,268 and 4,199 patients), inhalational agent requirements, and current US legalization status.
8. Cannabinoids and general anesthetics: revisiting molecular mechanisms. Anesth Analg. 2025. Notes consistently increased requirements for GABAergic agents in humans alongside divergent animal findings.
9. Randomized, single-blind study of propofol requirement for laryngeal mask airway insertion in regular cannabis users versus non-users, as summarized in perioperative clinician guidance.
10. Sajdeya R, Treggiari MM, Narouze S. Review of cannabis use and propofol anesthesia: recent insights and clinical implications. Curr Opin Anaesthesiol. 2025. PMID 40583839. States that no evidence currently supports causality and mechanisms remain unknown.
11. Perioperative considerations for the patient utilizing cannabis. Iowa Department of Health and Human Services. Covers synthetic cannabinoid coagulopathy not corrected by vitamin K or FFP, and THC catecholamine and dysrhythmia effects.
12. Perioperative repercussions of cannabis use — implications for GI endoscopy sedation. PMC12525429. Includes Canadian prevalence data and the endoscopy subgroup analysis.