Should you stop Mounjaro or Wegovy before surgery or an anaesthetic?
What the MHRA and UK anaesthetists advise for tirzepatide (Mounjaro), semaglutide (Wegovy, Ozempic) and other GLP-1 medicines before an operation.
Written for the United Kingdom. Other country versions are coming.
In the UK, the advice is to keep taking it unless your doctor says otherwise. The MHRA and eight UK anaesthesia and diabetes bodies advise continuing GLP-1 medicines around surgery. Tell your anaesthetist, because a slow stomach raises the risk of breathing in stomach contents.
Key takeaways
- UK advice is not to stop routinely: a 2025 consensus of eight UK bodies says patients should keep taking GLP‑1 medicines throughout the time around surgery.1
- The MHRA says these medicines slow stomach emptying, so food may remain despite fasting and could enter the lungs under general anaesthesia or deep sedation.2
- Private prescriptions may not appear in NHS records, so the MHRA asks every patient on a GLP‑1 to tell the anaesthetist before a procedure.2
- The UK consensus cites data showing a week off the medicine still left a high risk of food in the stomach, and pauses of up to 3 weeks still showed more.1
- By December 2024 the MHRA had received a very small number of Yellow Card reports of aspiration during surgery on these medicines, one with pneumonia.2
On this page
- Why does a GLP-1 matter for an anaesthetic?
- Should you stop Mounjaro or Wegovy before surgery?
- What will the hospital team do differently?
- Who is at higher risk?
- Why tell the team, especially if private?
- What if you have type 2 diabetes?
- Can weight-loss jabs be used to get ready for surgery?
- Questions people ask
- How we researched this
Why does a GLP-1 matter for an anaesthetic?
These medicines slow how fast your stomach empties. Under a general anaesthetic or deep sedation, food left in the stomach can come up and reach the lungs.2
- GLP‑1 medicines are prescription-only in the UK. On the NHS or privately, a healthcare professional has to assess you before a prescription is issued.3
- The label facts here come from the UK product information (the SmPC, the official label each maker publishes on the electronic Medicines Compendium). Where we use a US or EU label instead, we say so.
- Never stop or change a dose before an operation on your own. The MHRA says to keep taking your prescribed medicine and to discuss any change with your doctor first.3
- Every risk of these medicines is in Guide 5: Side effects and risks.
- This post describes labels, guidance and trials. It is not a plan for your treatment, and no dose or brand guarantees any result.
That is called pulmonary aspiration: stomach contents going into the airways and lungs. It can lead to a serious chest infection (aspiration pneumonia).2 All GLP‑1 medicines, and tirzepatide (Mounjaro), slow stomach emptying.2
This is why you are asked not to eat before an operation. The MHRA warns that on these medicines some food may remain "despite preoperative fasting".2 The UK labels for Mounjaro and Wegovy carry the same warning.4,5
How often has it happened? By 12 December 2024 the MHRA had received "a very small number" of Yellow Card reports of aspiration during surgery. One led to aspiration pneumonia.2 A UK consensus statement reviewed the published case reports. In the ones it described, every patient had obesity and had fasted properly.1
Should you stop Mounjaro or Wegovy before surgery in the UK?
No routine stop is advised. The MHRA says to take your medicine as usual, and UK anaesthesia and diabetes groups advise continuing it throughout the time around surgery.1,3
In January 2025, eight UK professional bodies published a joint statement. They include the Royal College of Anaesthetists and the Centre for Perioperative Care. Their advice: "Patients should continue to take glucagon-like peptide-1 receptor agonists throughout the peri-operative period."1
The MHRA says the UK labels give no guidance on withholding these medicines before surgery.2 A European review tried to set a pause time, or new fasting rules. The evidence was too limited, so anaesthetists keep the flexibility to judge each case.2
Why not just stop for a week? The consensus says the medicine stays in the body for a long time. Stopping weekly semaglutide 1 mg for a week leaves blood levels like someone still taking 0.5 mg.1 It cites data where even a week off still left "a high risk" of food in the stomach. Pauses of up to 3 weeks were still linked to a fuller stomach.1
Stopping has its own costs. High blood sugar around surgery is linked to longer stays, wound infection and kidney injury.1 Weight also tends to return after stopping, as covered in what happens when you stop.
What will the hospital team do differently?
They assess your own aspiration risk and may change the anaesthetic. The UK statement makes eight recommendations, starting with a shared decision with you.1
- Talk it through. The risk and the ways to reduce it should be discussed with you, in a shared decision.1
- Normal fasting rules still apply. Patients and clinicians should stick to the recommended fasting guidelines.1
- Symptoms aren't enough to judge. Stomach symptoms alone should not be used to decide whether your stomach is empty.1
- Another kind of anaesthetic. Regional anaesthesia, such as numbing one part of the body, should be considered first where it suits the operation.1
- A quick scan. A bedside ultrasound of the stomach may be used before you go to sleep.1
- Airway care. Options include a breathing tube, medicines that speed the stomach, sitting you head-up, or a tube to empty the stomach.1
The MHRA says the pre-procedure instructions and the anaesthetic technique may need to change.2 It asks teams to spot the risk early, ideally at the pre-assessment clinic.2
Who is at higher risk?
The MHRA names people with diabetic gastroparesis, obesity or reflux, and anyone with symptoms of a slow stomach. Recently starting or raising a dose may matter too.1,2
- A slow stomach from diabetes (diabetic gastroparesis), or reflux (gastro-oesophageal reflux disease).2
- Symptoms of slow emptying, such as feeling sick, vomiting or stomach pain.2
- A recent start or dose increase. The UK consensus says slower emptying "might be of particular clinical relevance" then. Of the case reports that gave treatment length, 4 of 5 described a recent start.1
- Emergency surgery, or sedation without a breathing tube. The consensus counts both as extra risk factors.1
The consensus points out that everyone on these medicines has at least two risk factors: the medicine, plus diabetes or obesity.1 Among surgical patients in general, some data suggest 6% to 16% who fasted properly still had enough in the stomach to raise the risk.1
Builds a printable list for your pre-assessment visit, including the medicines you take now. No sign-up.
Why tell the team, especially if your prescription is private?
Private prescriptions may not appear in your NHS records. The MHRA asks teams to ask directly, and asks patients to tell their anaesthetist before any procedure.2,3
The MHRA's advice to patients: "make sure you inform your healthcare team including the anaesthetist".2 It warns staff that private prescriptions "may not always be included" in medical notes.2 It also says some people bought these medicines for cosmetic weight loss and may not mention it unless asked.2
The details that matter are the ones on the risk lists: which medicine, the dose, and whether you started or increased it recently.1,2 The warning covers any procedure under general anaesthesia or deep sedation, not only operations.2
What if you have type 2 diabetes?
Stopping a GLP‑1 could let blood sugar rise around surgery, which the UK consensus links to harm. Some other diabetes tablets follow a different rule.1
The UK consensus treats SGLT‑2 inhibitors (tablets such as dapagliflozin or empagliflozin) differently. It says they should be left out the day before and the day of a procedure, because of a risk of ketoacidosis.1 That advice is for SGLT‑2 tablets, not for GLP‑1 injections.1
The consensus also notes that people using GLP‑1 medicines for weight can still get high blood sugar from the stress of surgery. It says their sugar should be checked regularly.1 The type 2 diabetes path covers the rest of your medicines.
Can weight-loss jabs be used to get ready for surgery?
In Wales, yes, for some people. Since October 2025, the Welsh NHS has offered tirzepatide to people waiting for time-sensitive surgery or an organ transplant.6
The Welsh Government says the same route covers women seeking fertility treatment. It also covers people with severe asthma, severe sleep apnoea or cancer, where weight loss would improve treatment.6 We found no matching surgery-waiting route in the NICE guidance for England.7
For NHS access by nation, see Mounjaro on the NHS.
- Breathing in stomach contents under general anaesthetic or deep sedation: the UK Mounjaro and Wegovy labels warn of it.4,5
- Stomach effects are very common (more than 1 in 10) on the UK Wegovy and Mounjaro labels, mostly while the dose is going up.4,5
- Pancreatitis is uncommon (1 in 100 to 1 in 1,000) on both UK labels.4,5
- Low blood sugar is more likely when these medicines are taken with insulin or a sulfonylurea, the labels say.4,8
- Dehydration from vomiting or diarrhoea can harm the kidneys.4
Questions people ask
Should I stop Mounjaro before surgery?
Not routinely. The MHRA says to keep taking your prescribed medicine and not to stop without discussing it with your doctor. UK anaesthesia and diabetes bodies advise continuing it throughout.1,3
How many days before surgery should I stop Wegovy?
UK guidance gives no number of days. The MHRA says the UK labels contain no withholding advice, and the UK consensus advises continuing, because short pauses did not clearly empty the stomach.1,2
Do I need to tell the anaesthetist I take Mounjaro?
Yes. The MHRA asks patients to tell their healthcare team, including the anaesthetist, because the medicine slows stomach emptying and may change how the anaesthetic is given.2
Does this apply to a colonoscopy or endoscopy?
The MHRA warning covers procedures under general anaesthesia or deep sedation, not only operations.2 The team decides how to manage your sedation.
Does it matter that I bought it privately?
It can. The MHRA says private prescriptions may not appear in medical notes, so the team may not know unless you tell them.2
Shorter answers: Should I stop Mounjaro before surgery?
How we researched this
On 12 Oct 2026 we read the MHRA’s January 2025 Drug Safety Update on aspiration and its patient guidance, updated February 2026. We read the January 2025 UK consensus statement in full. We checked the aspiration warning in the UK Mounjaro and Wegovy labels.
This is a new UK topic with no India equivalent. We kept to UK guidance and did not cover other countries’ advice. The consensus authors declare their own interests in the paper; it is a Delphi expert agreement, not a trial.
Before you move on
- UK advice is to keep taking your GLP‑1 around surgery unless your team says otherwise.
- Tell your anaesthetist, with the dose and day of your last injection, especially if it is private.
- The team may change the anaesthetic, not your medicine.
- SGLT‑2 diabetes tablets follow a different rule.
More from the UK blog
The monthly UK update
An independent guide to GLP‑1 medicines. We don't sell medicines, take drug-company money or earn clinic commissions. Once a month: NHS access changes, approvals, safety notices and recalls. How we write
Sources
- El-Boghdadly K, Dhesi J, Fabb P et al. Elective peri-operative management of adults taking glucagon-like peptide-1 receptor agonists, glucose-dependent insulinotropic peptide agonists and sodium-glucose cotransporter-2 inhibitors: a multidisciplinary consensus statement (Association of Anaesthetists, Association of British Clinical Diabetologists, British Obesity and Metabolic Surgery Society, Centre for Perioperative Care, Joint British Diabetes Societies for Inpatient Care, Royal College of Anaesthetists, Society for Obesity and Bariatric Anaesthesia and UK Clinical Pharmacy Association). Anaesthesia 2025;80(4):412–24. Box 1 and discussion. DOI · PMC11885194 · PMID 39781571
- MHRA. Drug Safety Update: GLP‑1 and dual GIP/GLP‑1 receptor agonists: potential risk of pulmonary aspiration during general anaesthesia or deep sedation. Volume 18, issue 6, 28 January 2025. gov.uk
- MHRA (Medicines and Healthcare products Regulatory Agency). GLP‑1 medicines for weight loss and diabetes: what you need to know. First published 5 June 2025, updated 5 February 2026. gov.uk
- Eli Lilly. Mounjaro KwikPen (tirzepatide): UK summary of product characteristics (SmPC, the UK label), date of revision 29 August 2026. Sections 4.2, 4.4, 4.5, 4.6, 4.8, 5.2, 6.4. emc
- Novo Nordisk. Wegovy FlexTouch (semaglutide) pens: UK summary of product characteristics (SmPC), date of revision 09/2026. Sections 4.1, 4.2, 4.4, 4.5, 4.6, 4.8, 5.1, 5.2, 6.3, 6.4. emc
- Welsh Government. People waiting for time-sensitive surgery get weight loss drugs on NHS. 23 October 2025. gov.wales
- NICE. Tirzepatide for managing overweight and obesity (TA1026), recommendations 1.1 and 1.2. Published 23 December 2024, last updated 1 September 2025. nice.org.uk
- Novo Nordisk. Ozempic (semaglutide) pens: UK SmPC, date of revision 07/2026. Sections 4.1, 4.2, 4.4, 4.6, 4.8, 5.1, 5.2. emc
- NHS. When to call 999. Page last reviewed 3 February 2023. nhs.uk
- MHRA. Drug Safety Update: GLP‑1 receptor agonists and dual GLP‑1/GIP receptor agonists: strengthened warnings on acute pancreatitis, including necrotising and fatal cases. Volume 19, issue 6, 29 January 2026. gov.uk
- NHS. Dehydration. Opened 12 October 2026. nhs.uk
- NHS. When to use NHS 111 online or call 111. Opened 12 October 2026. nhs.uk
- nidirect (Northern Ireland government). GP out of hours service. Opened 12 October 2026. nidirect.gov.uk
Last checked 12 Oct 2026 · Next review due 12 Oct 2027 · Report an error
How this post was made. Written by the GLP Guidebook team from the sources above. It's general information, not medical advice. Talk to a qualified doctor, nurse or pharmacist before starting, stopping or changing any medicine. How we write