Do not stop or change your medicine on your own. Tell your surgeon, anaesthetist or endoscopy team that you take Mounjaro, Wegovy, the Wegovy pill or Foundayo as early as possible. Current UK consensus guidance (2025) is that most people can continue treatment, with a perioperative risk assessment and, where needed, extra precautions such as a liquid diet beforehand or a modified anaesthetic technique. The right plan depends on you, the procedure and your hospital’s local policy.
GLP-1 medicines slow the rate at which the stomach empties. This is part of how they reduce appetite, but it also means food and fluid may stay in the stomach longer than expected, even after the usual fasting period. Under general anaesthesia or deep sedation, your protective airway reflexes are reduced. If stomach contents come back up, there is a risk they could be inhaled into the lungs, called pulmonary aspiration. It is uncommon, but it can be serious. The same slowed emptying is behind the nausea and fullness many people notice on treatment: see our nausea guide and our how it works page.
In January 2025 the MHRA published a Drug Safety Update highlighting this risk and the possibility of residual gastric content despite fasting, and advising that patients be assessed before procedures involving anaesthesia or sedation. Since then, UK anaesthetic and surgical bodies have worked on shared guidance.
How the Advice Has Changed| Approach | What it said | Status |
|---|---|---|
| Earlier cautious approach | Stop weekly GLP-1 medicines around a week before surgery | Used widely at first Stopping can affect blood sugar and weight, and evidence it prevents aspiration was limited |
| 2025 UK consensus | Most people can continue; carry out a risk assessment and use mitigation where needed | Current direction |
| Local hospital policy | Each trust may set its own pre-operative instructions | Follow your team Can still differ |
The 2025 UK consensus recommended that treatment can generally be continued, that patients should be risk-assessed individually, and that mitigation should be used where the risk is higher. People with diabetes who take an SGLT2 inhibitor have separate, long-established advice to omit it before surgery, which is a different issue from the GLP-1 medicine.
Important
Recommendations are changing and different hospitals may follow different protocols. Your anaesthetist has the final say on your care. If instructions you receive conflict with this guide, follow your clinical team.
Treatment differences matter less than you might think: the concern applies to the whole class, whether you take an injection such as Mounjaro or Wegovy, or a tablet such as the Wegovy pill or Foundayo. Our decision guide and pill or injection comparison explain how they differ in other ways.
Why Not Simply Stop for a Few Weeks to Be Safe?It sounds like the cautious option, but it has trade-offs. Because these medicines build up and wear off over days to weeks, a short pause may not fully reverse the slowed stomach emptying, so stopping is not a guarantee of an empty stomach. Pausing can also lead to appetite returning, loss of blood sugar control in people with diabetes, and a need to re-titrate afterwards, with the nausea that can bring. That is why the 2025 consensus favours assessing each person rather than applying one rule to everyone. If you have type 2 diabetes, see our guides on Mounjaro and type 2 diabetes and Foundayo and type 2 diabetes.
Tell anyone who will be giving you anaesthesia, sedation or a procedure that involves an empty stomach. Do not assume it is on your record. Give the name of the medicine (Mounjaro, Wegovy, the Wegovy pill or Foundayo), your current dose and the day you take it. If you are not sure of your dose, check your latest prescription or ask your pharmacist, and bring the pen or packaging if you can.
| Procedure | Who to tell | Why |
|---|---|---|
| Planned surgery under general anaesthetic | Surgeon and pre-assessment nurse; anaesthetist | Risk assessment and fasting plan |
| Endoscopy or colonoscopy with sedation | Endoscopy unit when booking | A full stomach affects the view and sedation risk; bowel preparation may be affected |
| Dental work with sedation or general anaesthetic | Dentist and sedation provider | The same aspiration concern applies |
| Minor procedures under local anaesthetic only | Mention it anyway | Usually low concern, but they should know |
| Emergency surgery | Tell the team immediately | They will assume a full stomach and plan accordingly |
Your anaesthetist will weigh up your own risk. Factors that raise the risk include being in the dose-escalation phase, higher doses, recent dose increases, gastrointestinal symptoms such as nausea, vomiting, bloating or abdominal pain, and conditions that independently slow gastric emptying, such as diabetes complications. Depending on the assessment they may:
- Ask you to follow a liquid or low-residue diet for a period before the procedure
- Ask you to continue as normal with standard fasting
- Check the stomach on the day, for example with an ultrasound scan
- Use a technique that assumes a full stomach, such as rapid sequence induction
- In some cases, advise a planned pause of the medicine, particularly if you are at higher risk
Each of these is a clinical decision made by your team. The point is that there are several options, and stopping the medicine is only one of them. Being in the dose-escalation phase is one of the factors that raises risk, so it helps to know where you are on your schedule: see the dose guides for Mounjaro, Wegovy, the Wegovy pill and Foundayo.
A Typical Timeline- 1When the procedure is bookedTell the surgeon or booking team you take a GLP-1 medicine, the name, the dose and the day you take it.
- 2Pre-assessmentRepeat this to the nurse and ask for specific written instructions on whether to take your next dose.
- 3The week beforeFollow any diet or medicine instructions exactly. Contact the team if you are unsure.
- 4The day beforeFollow fasting and any liquid-diet instructions. Report new nausea, vomiting or abdominal symptoms.
- 5The day of the procedureTell the anaesthetist again. Say when you last ate, drank and took your medicine, and report any symptoms.
- 6AfterwardsAsk when to restart. Restart as instructed, and tell your prescriber if you have missed more than one dose.
If your team asks you to skip a dose, that is a clinical decision for the procedure and should be followed. Ask for clear written instructions on which dose to skip and when to restart. If a pause is longer than a few doses, restarting may need to be done at a lower dose to limit side effects, so contact your prescriber. Our missed Mounjaro dose guide, missed Wegovy pill dose guide and the dose schedules for Mounjaro, Wegovy, the Wegovy pill and Foundayo explain how restarting usually works.
For Foundayo, which is a daily tablet, the same principle applies: tell your team, and follow their written instructions on whether to take it on the day. If you have been off any GLP-1 medicine for a week or more, speak to your prescriber before restarting, as the dose may need to be re-titrated. See how to take Foundayo and how to take the Wegovy pill.
Blood Sugar and Other MedicinesIf you take other medicines, particularly for diabetes, the plan needs to cover them too. Do not adjust insulin or sulfonylureas on your own, as pausing a GLP-1 medicine can change your blood sugar. People taking SGLT2 inhibitors are usually told to stop them a few days before surgery because of the rare risk of ketoacidosis. Make sure your pre-assessment team has a full list of everything you take.
What to Expect After SurgeryNausea and reduced appetite are common after anaesthesia and may overlap with the medicine’s own effects. Eat small amounts, drink fluids, and follow your surgical team’s instructions. Report persistent vomiting, severe abdominal pain, a swollen abdomen or being unable to keep fluids down, as these need prompt assessment. See our guides on nausea and constipation, which is also common after surgery and some pain relief.
Think about nutrition too. Wound healing depends on adequate protein and fluids, so recovery is not the time to push a large calorie deficit. Our nutrition guide and calorie deficit calculator can help, and keeping your protein up helps protect muscle: see the Mounjaro, Wegovy, Wegovy pill and Foundayo muscle preservation guides.
| Warning sign after surgery | What to do |
|---|---|
| Persistent vomiting or unable to keep fluids down | Urgent Seek medical advice promptly |
| Severe abdominal pain, swollen abdomen | Urgent Seek medical attention |
| Constipation lasting several days | Soon Speak to your pharmacist or GP |
| Missed more than one dose | Prescriber Ask before restarting at your previous dose |
Many people take these medicines in preparation for procedures such as joint replacement, where a lower weight reduces risk. This is a legitimate use. Make sure your surgical team knows you are on treatment and agrees the plan, including the point at which you should continue, adjust or pause. You can check your eligibility with our BMI calculator or read about NHS eligibility.
Questions to Ask Your Surgical or Anaesthetic Team- Should I take my next dose before the procedure?
- Do I need a liquid diet beforehand, and for how long?
- Will you check my stomach on the day?
- When should I restart, and at what dose?
- Who do I contact if my plan changes?
The bottom line
The aim is not to stop your treatment automatically, but to give your anaesthetic team the information they need to keep you safe. Tell them early, ask for written instructions and follow them. Questions about your treatment? See our weight loss consultation or our full guide library.
Questions About Your Treatment Before a Procedure?
Our GPhC-registered pharmacy team can help you prepare the right questions for your surgical team and review your plan.
Start Your Free Online Consultation → Use code SWITCH10 if you're switching from another provider Happy Pharmacy is a GPhC-registered pharmacy (No. 9013192) — Superintendent Pharmacist: Palvinder Deol — Rated 4.8★ Excellent on Trustpilot- MHRA. GLP-1 and dual GIP/GLP-1 receptor agonists: potential risk of pulmonary aspiration during general anaesthesia or deep sedation. Drug Safety Update, January 2025.
- Multisociety UK consensus guidance on the perioperative management of patients taking GLP-1 receptor agonist and dual GIP/GLP-1 receptor agonist medicines, 2025.
- Mounjaro® (tirzepatide) UK Summary of Product Characteristics, section on pulmonary aspiration during general anaesthesia or deep sedation, electronic Medicines Compendium (emc).
- Wegovy® (semaglutide) UK Summary of Product Characteristics, emc.
- Foundayo® (orforglipron) UK Summary of Product Characteristics, emc.
- Centre for Perioperative Care. Guidance on the perioperative management of medicines.