Pulse ·
GLP-1 medications and surgery: disclose even if not GP-prescribed
A study of over 47,000 surgical patients in the journal Anaesthesia found GLP-1 users were 11 times more likely to aspirate stomach contents under general anaesthetic. GLP-1 drugs slow gastric emptying, so food may remain in the stomach even after standard fasting.
ANZCA is urging all patients — including those using unapproved peptides obtained outside their GP's knowledge — to disclose use before any surgical procedure. Anaesthetists can adjust their approach when they know; they cannot when they don't.
This applies to Ozempic, Wegovy, Mounjaro, and similar medications for diabetes or weight management. Discuss timing and fasting with your GP or anaesthetist before surgery.
There is a version of this story that is familiar: GLP-1 medications slow stomach emptying. That has been known since these drugs entered widespread use. What has been less clear, until recently, is whether that mechanism creates a meaningful surgical risk — and for whom.
A new study of more than 47,000 UK surgical patients, published in the journal Anaesthesia, has put a number on it. People taking GLP-1 drugs were 11 times more likely to regurgitate or aspirate stomach contents under general anaesthesia than people not on these medications. Most episodes involved regurgitation as patients woke from anaesthesia. Pulmonary aspiration — stomach contents entering the lungs — is rare but potentially life-threatening, and it is the reason standard pre-operative fasting guidance exists.
The complication with GLP-1 medications is that fasting as normal is not enough. Because these drugs delay gastric emptying, food consumed before the fasting window may not have cleared the stomach by the time of surgery. The stomach can appear empty by conventional fasting criteria when it is not.
The Australian and New Zealand College of Anaesthetists (ANZCA) has responded with a direct message: tell your anaesthetist you are on these medications. Tell them even if you were not prescribed them by your GP. Tell them if you obtained them from a weight-loss clinic, a gym, or online. Tell them if you are using unapproved injectable peptides.
The hidden-use problem
About half a million Australians are estimated to regularly use GLP-1 medications. Almost half of those pay out of pocket, and many are obtaining them through pathways outside their usual general practice relationship. Some patients use unapproved peptides — including retatrutide — sourced via online clinics, compounding pharmacies, or gym networks. The TGA has issued prior warnings about these products.
The clinical consequence is that anaesthetists are sometimes performing procedures without knowing that a patient’s gastric emptying is pharmacologically delayed. ANZCA president Dr Tanya Selak described it plainly: “This is a situation that we can manage, but we need to know about it.”
Professor Michael Horowitz from the University of Adelaide, who studies gastric emptying, has described the situation as “an accident waiting to happen” — not because the risk is catastrophic for every patient, but because disclosure gaps mean the risk cannot be consistently managed.
Both-and: stopping is not automatically safer
The instinctive response — stop the medication before surgery — is more complicated than it sounds.
For people on GLP-1 drugs for type 2 diabetes management, stopping without medical input can destabilise blood glucose in the lead-up to surgery, which carries its own risks. Some GLP-1 medications also confer kidney-protective benefits that are interrupted by stopping. Professor Horowitz described advising patients to stop a week before surgery as “demonstrably stupid” — strong language, but it reflects the real clinical tension.
The right question is not “should I stop?” but “what plan is appropriate for me, given my indication, my surgery, and my current medication?” That is a conversation for the prescribing doctor and the anaesthetist together — not a unilateral patient decision, and not a blanket rule.
ANZCA’s revised guidance for GLP-1 users suggests taking clear fluids only for the 24 hours before surgery, then fasting from six hours prior — stricter than standard fasting. But even that guidance should be confirmed with the treating team, because individual circumstances vary.
2 cents
If you are on a GLP-1 drug — Ozempic, Wegovy, Mounjaro, or any injectable weight-management or diabetes medication — and you have a surgical procedure coming up, the single most important action is to tell your anaesthetist. Not just the doctor who prescribed it. The anaesthetist, directly, at the pre-operative assessment.
The same applies if you are using unapproved injectable peptides, whether for weight management, muscle recovery, or any other purpose. ANZCA’s message was that there is no judgement. Anaesthetists cannot adjust their approach for a risk they don’t know exists.
If you are unsure whether what you are taking counts, discuss it with your GP. RACGP expert committee member Dr Michael Tam put it plainly: “GPs want to know about the medicines being used” — even if they are not the prescribing doctor. The conversation can happen in any direction; it just needs to happen before the anaesthetic does.
Verdict: yes — the evidence is solid, the clinical action is clear, and half a million Australians are on these medications. Worth knowing about.
Sources cited
Frequently asked questions
-
Should I stop my GLP-1 medication before surgery?
This is a question to discuss with the doctor who prescribed it and your anaesthetist — not a decision to make alone. Stopping GLP-1 medications can be dangerous for people using them to manage type 2 diabetes, and may mean losing associated kidney-protective benefits. The timing question is genuinely complex, and the current recommendation is to disclose use and plan together rather than either continuing without disclosure or stopping abruptly.
-
What about unapproved peptides from a gym or online clinic?
The same gastric-emptying concern applies. ANZCA specifically flagged unapproved peptides — including retatrutide and similar compounds — in its guidance. The TGA has previously issued warnings about these products. The key action is to tell your anaesthetist, without fear of judgement. ANZCA's message was direct: there is no judgement, they are partners in your care.