GLP-1 medicines and surgery: what to tell your anaesthetist

Taking GLP-1 medications before surgery is something your anaesthetist needs to know about. Semaglutide (Wegovy, the Wegovy pill, Ozempic and Rybelsus), tirzepatide (Mounjaro) and orforglipron (Foundayo) all slow stomach emptying, so food and drink can still be there after the usual fast; under general anaesthesia or deep sedation, that raises the risk of stomach contents entering the lungs. In January 2025 the MHRA asked everyone on these medicines to tell their healthcare team, including the anaesthetist, before any surgery or procedure under general anaesthesia or deep sedation, and not to stop the medicine without a doctor’s advice.

This is information only, not medical advice: these are prescription-only medicines, a prescriber decides whether one suits you, and your anaesthetic is your treating team’s decision.

Why GLP-1 medications before surgery matter

The MHRA’s Drug Safety Update of 28 January 2025 puts it plainly: GLP-1 and dual GIP/GLP-1 receptor agonists “are known to cause delayed gastric emptying, which may increase the risk of residual gastric contents despite preoperative fasting”. If those contents come up while you are deeply sedated or anaesthetised, they can enter the airways and lungs: pulmonary aspiration, which can lead to aspiration pneumonia.

After a European review, the warning went into the product information for the whole class. The SmPCs for Mounjaro, Wegovy and Wegovy tablets say cases of pulmonary aspiration have been reported in patients on GLP-1 receptor agonists under general anaesthesia or deep sedation, and that the increased risk of residual gastric content should be considered beforehand. Foundayo was authorised in 2026, after that update, but its SmPC carries an equivalent warning: aspiration has been reported in patients on long-acting GLP-1 receptor agonists under general anaesthesia or deep sedation, and should be considered before such procedures; it also notes that the delay is largest after the first dose and diminishes over time.

As of 12 December 2024 the MHRA had received a very small number of Yellow Card reports of aspiration during surgery on these medicines, including one case of aspiration pneumonia: rare, but serious enough to plan around.

Which procedures count?

Neither the MHRA update nor the SmPCs list procedure types: the wording is any surgery or procedure under general anaesthesia or deep sedation, not only major operations. The examples are ours, not the MHRA’s: a day-case operation under general anaesthetic falls within it; a sedated endoscopy, colonoscopy or dental treatment may, depending on how deep the sedation is, which the unit decides. Whoever sedates you needs to know.

Who decides whether to pause, and why not to stop on your own

The MHRA’s advice to patients is to take prescribed medicines as usual and not to stop without first discussing it with a doctor. The same update explains why the decision sits with the team:

• the UK SmPCs give no guidance on withholding these medicines before surgery or deep sedation;
• a European review asked whether a specific time to pause, new fasting rules or a test for an empty stomach could be recommended, found limited evidence to support further recommendations, and concluded that anaesthetists should keep the flexibility to assess each person individually;
• the Association of Anaesthetists’ multidisciplinary consensus statement of January 2025, the MHRA notes, advises taking the medicine as normal, daily or weekly.

So the anaesthetist weighs your risk, allowing for diabetic gastroparesis, a higher body weight, acid reflux and any symptoms of delayed gastric emptying, and may change the fasting instructions or the technique.

What to tell the pre-op team, and when

The MHRA asks hospitals to identify the risk early, specifically at pre-assessment clinic, and warns that private prescriptions are not always in the notes, so staff are told to ask. Do not wait to be asked. Tell them:

• the medicine and dose, and whether it is for weight or diabetes;
• weekly injection or daily tablet, your usual injection day, and the date of your last dose;
• how long you have taken it and whether the dose rose recently;
• that it is a private prescription, if it is;
• any diabetes, reflux or gastroparesis, and every other medicine, including insulin or a sulfonylurea;
• any current stomach symptoms.

Say it at pre-assessment, when booking an endoscopy or sedation appointment, and again on the day; tell them if you start or step up a dose in between. Dose ladders are on our Mounjaro, Wegovy, Wegovy pill and Foundayo pages.

Fasting, and the symptoms to mention

On these medicines, the MHRA says, food and drink may still be present despite the usual fast, so the pre-procedure instructions and anaesthetic technique may need to change. Follow the fasting instructions your own team gives you for this procedure. If you take the Wegovy pill (empty stomach, a sip of water, a 30-minute wait) or Foundayo, ask whether and when to take your tablet on the day.

The MHRA names nausea, vomiting and abdominal pain as symptoms of delayed gastric emptying that may raise the risk, and reflux disease as a condition that does. Mention these if you have them, even mildly, along with bloating or feeling full long after a meal. They are commonest after starting or increasing a dose; see managing GLP-1 side effects.

Afterwards: restarting is your prescriber’s call

If nothing was paused, carry on as prescribed. If the team did ask you to delay a dose, ask them and your prescriber when to take the next one. The SmPCs have missed-dose rules (a missed Mounjaro dose can be given within 4 days and a missed Wegovy injection within 5, after which it is skipped; a missed Wegovy tablet is skipped; a missed Foundayo tablet is taken when remembered, never two in one day), and the Wegovy SmPC says that after more than one missed dose, restarting at a lower dose should be considered: a prescriber’s judgement.

Tell the team if you feel sick or vomit afterwards. Suspected side effects, including problems around anaesthesia, can be reported to the MHRA Yellow Card scheme by patients and carers; the MHRA specifically asks for reports of aspiration and other surgical complications. More answers are on our FAQ page and in GLP-1 long-term safety.

Frequently asked questions

Related reading

• Managing GLP-1 side effects
• What happens when you stop a GLP-1 medicine?
• GLP-1 long-term safety