Know Your Script
Checked by us, not by a practitioner. Every legal statement below was checked against the primary instruments listed at the foot of this page — each one retrieved from the government register that publishes it, at the version named, and read. That is what the last-checked date means here. It does not mean a solicitor, barrister or other credentialed professional has reviewed this page; none has. If you are a professional willing to change that, the terms are here.

Australia-wide

Do I have to tell my anaesthetist about my prescription?

There is no law on this

The short answer

There is no law requiring it, and a clear clinical reason to do it. Published anaesthesia research has repeatedly found that regular cannabis users need measurably more anaesthetic agent to reach the same depth, and report more pain afterwards. Your anaesthetist cannot plan around what they have not been told.

General information, not advice. This page describes the law as at the last-checked date shown at the foot of it. It does not take your circumstances into account, and small differences in circumstances change outcomes. If a decision turns on this, speak to someone qualified about your own situation.

This page is not sourced to legislation, because there is none on point. No Australian statute answers this question. What follows is drawn from the peer-reviewed anaesthesia literature listed under Sources, and it is clinical evidence, not law — weigh it that way, and take it to your own treating team.

What the law actually says

No Australian statute governs telling a treating clinician about a prescribed medicine. This is a clinical safety question rather than a legal one, which is why this page cites medical literature instead of legislation.

What that literature says. A 2025 systematic review and meta-analysis pooling eight studies and 2,268 patients found propofol requirements significantly higher in cannabis users, both under general anaesthesia and for endoscopic sedation. A 2024 review in Anesthesia & Analgesia reports that clinical studies and case reports consistently show increased requirements for GABAergic anaesthetic drugs — isoflurane, sevoflurane, propofol and midazolam — and that human data shows cannabis users reporting higher postoperative pain scores and needing more opioid analgesia. A 2026 review adds that responses to opioids, ketamine and gabapentinoids may also differ, with proposed mechanisms including cytochrome P450 induction and CB1 receptor downregulation.

The practical conclusion those authors draw is the one this page makes: a 2020 review in Schmerz recommends that patients be asked before an operation about medical or recreational cannabis use. If you are not asked, tell them anyway.

This page deliberately quotes no doses. The figures in those studies describe what an anaesthetist administers, not anything you should do, and the whole point is that the decision belongs to the clinician who has the full picture.

What happens if it goes wrong

Withholding it means your anaesthetic is planned on incomplete information. The four papers below are about dose and pain, not about cancellation — none of them says a disclosed prescription leads to a procedure being called off, and none of them says it does not. What they describe is a plan that is adjusted once the anaesthetist knows.

If you are worried the disclosure itself will cost you the surgery date, say so to the pre-admission clinic when you disclose. That is a question about one hospital's practice, and the only people who can answer it are the ones running your list.

What to carry

  • Your pharmacy label, or a list naming the medicine, its strength and how often you take it.
  • The name and contact details of your prescriber.
  • The printable card at /tools/surgery-card/, filled in.

What to say

  • Tell the pre-admission clinic, not only the surgeon — your anaesthetist is usually a different person you meet on the day.
  • Say how often and how recently you have taken it, not just that you hold a prescription. Regularity is what the research turns on.
  • Mention it even if you have been asked to stop before surgery, and say when you actually last took it.

What not to do

  • Do not change or stop your dose on your own before surgery. Ask the person who prescribed it.
  • Do not assume it is already in your file. Say it out loud.
  • Do not downplay how often you take it. Under-reporting is the thing that makes the anaesthetic plan wrong.

Sources

Cite this page

Know Your Script, ‘What your anaesthetist needs to know before surgery’ (Australia-wide), https://www.knowyourscript.com.au/surgery/telling-your-anaesthetist/ (last checked 2026-08-15, publisher-checked, not reviewed by a practitioner).

Last checked against primary sources by the publisher: