If you're taking a GLP-1 weight loss medication and have any operation or procedure coming up, whether it's a knee replacement, having your gallbladder removed, a colonoscopy or wisdom teeth out under sedation, there's one conversation you shouldn't skip. To be clear, this isn't about weight loss surgery. It applies to any procedure where you'll have a general anaesthetic or sedation, for any reason.
This week the ABC reported that the Australian and New Zealand College of Anaesthetists (ANZCA) has issued a fresh warning to patients, after a large UK study found that people taking these medications were around 11 times more likely to regurgitate or inhale stomach contents under anaesthetic. ANZCA says some patients still aren't mentioning the medication before surgery because they forget, feel embarrassed, or don't want to admit to using unapproved peptides. As ANZCA president Dr Tanya Selak put it, "There is no judgement, we are partners in your care and that simple conversation can help us make the safest plan."
Here's what the research found, why it matters, and the simple steps that keep you safe.
Why these medications matter when you're under anaesthetic
GLP-1 medications help with weight loss partly by slowing down how quickly food leaves the stomach. That's part of why you feel full sooner and for longer. But it also means your stomach may not be empty before surgery, even if you've followed the usual fasting instructions.
Normally that wouldn't matter much. When you're awake, coughing and swallowing protect your airway. Under a general anaesthetic or deep sedation, those reflexes are switched off. If food or fluid comes back up from the stomach (regurgitation) and enters the lungs (pulmonary aspiration), it can cause a serious lung infection or injury. This is exactly why fasting before surgery exists, and why your anaesthetist wants to know about anything that could slow stomach emptying.
What the new study found
The study, led by researchers at King's College London and published in the journal Anaesthesia, looked at more than 47,000 patients having all kinds of planned and emergency procedures across the UK. Around 1,350 of them were taking a GLP-1 medication.
"11 times more likely" sounds frightening. How big is the risk really?
As always, a relative risk only makes sense once you know how often the problem happens in the first place.
•            Among people taking a GLP-1 medication, about 1 in 71 had regurgitation or aspiration, or roughly 14 in every 1,000.
•            Among everyone else, it was about 1 in 800, or just over 1 in every 1,000.
Most of those events in the GLP-1 group were regurgitation without anything reaching the lungs. True aspiration into the lungs was rare: 2 people out of about 1,350. So the large majority of people on these medications had their procedure without any problem. But the risk is real, it's higher than for other patients, and most importantly, it's one your anaesthetist can plan around, but only if they know.
A few caveats
This was an observational study, so it shows an association rather than proving the medication caused every event. People taking these medications are also more likely to have obesity or diabetes, both of which can affect stomach emptying and anaesthetic risk, and the researchers note that these factors are hard to fully separate. The study also relied on patients reporting their own medication use. Interestingly, more than 40% of the GLP-1 users had obtained their medication outside usual prescribing routes, which is a reminder that the people anaesthetists most need to hear from are sometimes the least likely to speak up.
Should you stop your medication before surgery?
Not on your own, and usually not at all. Current Australian guidance, developed by ANZCA together with the Australian Diabetes Society, the Gastroenterological Society of Australia and the National Association of Clinical Obesity Services (updated in 2025), generally recommends continuing these medications rather than stopping them. Stopping for a week or so may not be long enough to change how your stomach empties. The UK researchers estimate it could take three to four weeks for the effect to wear off. Stopping can also disrupt your progress (here's what happens when you stop weight loss injections) and, for people with diabetes, your blood sugar control.
Instead, the guidance focuses on preparation:
•            A clear fluid diet for the 24 hours before surgery: starting when you wake on the day before your procedure, followed by the standard fast. Clear fluids typically include water, clear broth, pulp-free juice, jelly and black tea or coffee, and your team should give you a list.
•            The usual fast: only water from six hours before your anaesthetic, and nothing by mouth for the final two hours, unless your team gives you different instructions.
•            A plan for people with diabetes: a day of clear fluids can affect blood sugar, so your doctor or endocrinologist may adjust your other diabetes medicines.
Your anaesthetist may also take extra precautions on the day, depending on your situation.
What should you do if you have a procedure coming up?
1.         Tell your whole team you're taking it. That includes your surgeon, the pre-admission nurse and your anaesthetist. Mention it for any procedure involving sedation or a general anaesthetic, including colonoscopy, gastroscopy, dental sedation and cosmetic procedures.
2.         Include anything you've bought yourself. If you're using peptides or injections from a gym, a website or overseas, say so. These products aren't approved in Australia and their contents can be uncertain, which is all the more reason your anaesthetist needs to know. They're there to keep you safe, not to judge.
3.         Know your dose and when you last took it. Many of these medications are taken weekly, so the timing of your last dose is useful information.
4.         Don't stop your medication without advice. Talk to your prescribing doctor well before your surgery date so there's time to make a plan together. If we prescribe your treatment, you can book a weight loss review consultation to plan around your procedure.
5.         Follow the fasting instructions exactly. If you're told to have clear fluids the day before, stick to them, and ask if you're unsure what counts.
6.         Make sure it's on record for emergencies. You can't prepare for unplanned surgery, so keep your medication on your phone's medical ID or a list in your wallet, and make sure someone close to you knows.
The bottom line
GLP-1 medications slow stomach emptying, and new research suggests this makes regurgitation and aspiration under anaesthetic noticeably more likely. The absolute risk is still low, and current Australian guidance is that most people can keep taking their medication, with a clear fluid day before surgery and the usual fast.
What makes the biggest difference is simply telling your treating team. Your anaesthetist has seen it all before and isn't there to judge. A quick conversation lets them plan the safest possible anaesthetic for you.
Frequently asked questions
Is this about weight loss surgery?
No. This applies to any operation or procedure with a general anaesthetic or sedation, such as joint replacements, abdominal surgery, colonoscopy, gastroscopy, dental sedation or cosmetic procedures. If you're taking a GLP-1 medication for weight or for diabetes, your anaesthetist needs to know, whatever the procedure is for.
Do I need to stop my weight loss injection before surgery?
Usually not. Current Australian guidance generally recommends continuing it, with a clear fluid diet for 24 hours beforehand and the usual fast. Your surgical team and prescribing doctor may give you different advice for your situation, so check with them well before the date.
Does this apply to a colonoscopy or gastroscopy?
Yes. Any procedure with sedation or a general anaesthetic counts. Tell the doctor doing the procedure and follow the preparation instructions they give you.
What if I bought peptides online or from a gym?
Tell your anaesthetist anyway. They ask about medications to keep you safe, not to judge you. Unapproved products can have uncertain contents and doses, which makes it even more important that your team knows.
Will my operation be cancelled if I mention it?
Telling your team usually means they can plan, not cancel. If the preparation hasn't been followed, they may decide it's safer to delay, which is far better than an avoidable complication.
What if I need emergency surgery?
You won't have time to prepare, so the most useful thing is that your team knows straight away. Keep your medication on your phone's medical ID or in your wallet, and make sure a family member knows what you take.
References
El-Boghdadly K, et al. Regurgitation and pulmonary aspiration in patients taking GLP-1 receptor agonists: a UK national multicentre study. Anaesthesia. 2026. [Exact title, author list and DOI to be confirmed against the journal.]
Australian Diabetes Society, Australian and New Zealand College of Anaesthetists, Gastroenterological Society of Australia, National Association of Clinical Obesity Services. 2025 ADS-ANZCA-GESA-NACOS clinical practice recommendations on the peri-procedural use of GLP-1/GIP receptor agonists. April 2025: https://www.anzca.edu.au/safety-and-advocacy/standards-of-practice/clinical-practice-recommendations-regarding-patients-taking-glp-1
Dalzell S, Cockburn P. Weight-loss GLP-1 jabs like Ozempic and unapproved peptides pose 'serious' surgery risk, doctors warn. ABC News. 7 October 2026: https://www.abc.net.au/news/2026-10-07/peptides-ozempic-surgery-warning/107233212
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