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Should I stop Mounjaro before surgery?

GLP Guidebook teamUpdated 12 Oct 20266 sourcesWritten from published sources
The short answer

Not usually, under UK advice. A 2025 consensus from 8 UK bodies, including the Royal College of Anaesthetists, says people on Mounjaro (tirzepatide) or GLP-1 medicines like Wegovy should keep taking them before planned surgery. The MHRA says to tell your healthcare team, including the anaesthetist, and not to stop without discussing it.

Before you go further
  • GLP‑1 medicines are prescription-only in the UK, not sold over the counter.6
  • The UK consensus asks each team to assess each person's risk, so the plan your own surgical team gives you comes first.1
  • The risks of these medicines are in Guide 5: Side effects and risks.

Why does a GLP‑1 matter for an anaesthetic?

Mounjaro and other GLP‑1 medicines slow how fast your stomach empties, so food can still be there after the usual fast before surgery.2

Under a general anaesthetic or deep sedation, stomach contents can get into your airways and lungs. Doctors call this pulmonary aspiration.3 The UK Mounjaro (tirzepatide) SmPC says cases have been reported in people on GLP‑1 medicines.4 In January 2025, the MHRA added this risk to the product information of every GLP‑1 and tirzepatide medicine.2 By 12 Dec 2024 it had received "a very small number of reports" of aspiration during surgery.2

What does UK guidance say about stopping before surgery?

A 2025 UK consensus from 8 professional bodies says to keep taking GLP‑1 medicines through the time around surgery, rather than stopping them.1

The bodies include the Royal College of Anaesthetists and the Centre for Perioperative Care.1 They say case reports show that stopping for a full week is not enough to remove the risk. One study saw bigger stomach volumes after up to 3 weeks off.1 The UK SmPCs give no advice on holding these medicines before surgery, the MHRA says.2

Instead, the consensus asks teams to:1

  • talk through the risk with you and decide together
  • keep to the usual fasting rules before surgery
  • assess each person's risk, sometimes with an ultrasound scan of the stomach
  • use anaesthetic methods that lower the chance of aspiration

The MHRA says your pre-procedure instructions or anaesthetic method "may" need to change.3 More detail is in Mounjaro and Wegovy before surgery and anaesthetic.

What should you tell your surgical team?

Tell your healthcare team and anaesthetist that you take a GLP‑1 before the procedure, and say if you started or raised the dose recently.3,1

The consensus says slower stomach emptying may matter most after starting or a dose increase, though newer studies question this.1 It warns that stomach symptoms alone are not a reliable sign of what's in your stomach.1 The MHRA's advice to patients is to keep taking the medicine as usual and "do not stop your treatment without first discussing this with your doctor".2 The UK leaflet also asks you to tell your doctor before surgery under anaesthesia.5

Two more points from the consensus. Diabetes tablets called SGLT2 inhibitors, a different medicine, should be missed the day before and the day of a procedure. People using a GLP‑1 for weight may get high blood sugar around surgery, so their sugar should be checked regularly.1

Questions for your pre-op assessment

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Related questions

When should I call 999 or 111 on a GLP‑1? Does Mounjaro stop the pill working? Can I get Mounjaro on the NHS? How long can Mounjaro stay out of the fridge?
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Sources

  1. 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, UK Clinical Pharmacy Association). Anaesthesia 2025;80(4):412-424. Full text read, Box 1. doi:10.1111/anae.16541 · PMID 39781571
  2. MHRA. GLP-1 and dual GIP/GLP-1 receptor agonists: potential risk of pulmonary aspiration during general anaesthesia or deep sedation. Drug Safety Update, 28 Jan 2025. gov.uk
  3. MHRA. GLP-1 medicines for weight loss and diabetes: what you need to know. Published 5 Jun 2025, updated 5 Feb 2026. gov.uk
  4. Eli Lilly. Mounjaro KwikPen (tirzepatide) UK summary of product characteristics (SmPC), date of revision 29 Aug 2026, sections 4.4, 4.5, 4.6, 6.3, 6.4 and 6.6. UK label. medicines.org.uk (emc)
  5. Eli Lilly. Mounjaro KwikPen (tirzepatide) UK patient information leaflet, last revised Aug 2026, sections 2, 3, 4 and 5. UK label. medicines.org.uk (emc)
  6. MHRA. First GLP-1 tablet for weight loss approved in the UK. Press release, 11 Jun 2026 ("As with all GLP-1 receptor agonists, this is a prescription-only medication"). gov.uk

Last checked 12 Oct 2026 · Next review due 12 Oct 2027 · Report an error

How this answer was made. Written by the GLP Guidebook team from the sources above. It's general information, not medical advice. Talk to a qualified doctor before starting, stopping or changing any medicine. How we write