Jump to: Should you stop Wegovy or Mounjaro before surgery? | What did the GLIMPSE study find? | How strong is the evidence? | Why does UK guidance still say to continue treatment? | Why are hospitals giving different advice? | What should you do before a planned procedure? | What happens if surgery is urgent? | Frequently asked questions | Take home message | References
Current UK clinical guidance says you should continue taking Wegovy (semaglutide) or Mounjaro (tirzepatide) before surgery, unless your anaesthetic team gives you a different instruction after assessing your individual risk3.
Don’t stop the medication yourself. Tell the pre-operative and anaesthetic teams what you’re taking, even if you receive it through a private prescription that may not appear in your NHS record.
A new UK study called GLIMPSE found regurgitation, where stomach contents come back up, or aspiration, where they enter the airway, in 1.41% of people who had used a GLP-1-based medication such as Wegovy or Mounjaro in the previous three months, compared with 0.12% of people who hadn’t used one.1
More than half of the regurgitation or aspiration cases among medication users happened as they woke from anaesthesia. This suggests anaesthetic teams may need to review how they protect the airway during this stage, including when the breathing tube is removed.1
However, GLIMPSE didn’t compare people who stopped Wegovy or Mounjaro with those who continued. Until a study does, there’s no reason to change the current UK guidance: continue taking the medication, tell your anaesthetic team, and follow any different instructions they give you for your procedure.
Important safety information: Wegovy and Mounjaro are prescription-only medications for managing obesity. Mounjaro is also licensed for type 2 diabetes. This article is for informational purposes only. Don’t change your medication or fasting plan without instructions from your anaesthetist, surgical team, prescriber, or diabetes team.
Should you stop Wegovy or Mounjaro before surgery?
You shouldn’t stop Wegovy or Mounjaro unless the team responsible for your procedure tells you to.
The current UK multidisciplinary consensus statement recommends continuing GLP-1 medications, including Wegovy, and dual GIP/GLP-1 medications such as Mounjaro, before elective surgery3.
Eight UK professional groups in anaesthesia, diabetes, obesity, surgery, and pharmacy produced the guidance. It recommends standard fasting alongside an individual assessment and precautions to reduce the chance of stomach contents entering the lungs.
Your anaesthetist may recommend a different plan because of the procedure, your symptoms, a recent dose increase, other medical conditions, or local hospital policy.
If you take Wegovy or Mounjaro for type 2 diabetes, stopping can raise your blood glucose (blood sugar) and may require changes to your other diabetes medication.
If you take Wegovy or Mounjaro only for weight loss and don’t have diabetes, stopping is unlikely to cause high blood sugar. But no study has shown that stopping either medication for one or two weeks reduces the chance of stomach contents entering the lungs during anaesthesia.
What did the GLIMPSE study find?
GLIMPSE was a prospective UK study. Before it began, researchers told hospitals to record whether each person had used a GLP-1-based medication and whether they regurgitated or aspirated during anaesthetic care.
The study screened 47,039 adults receiving anaesthetic care across 119 hospitals in all four UK nations between September and December 20251.
Of these, 1,348 had used a GLP-1 medication in the previous three months. Mounjaro accounted for 69.9% of use, and semaglutide accounted for 26.2%.
Regurgitation or aspiration was recorded in 19 of the 1,348 medication users, or 1.41%. It occurred in 57 of the 45,691 non-users, or 0.12%1.
That’s about 1 in 71 compared with 1 in 802, producing an odds ratio of 11.39.
Put another way, about 14 in every 1,000 people who had used a GLP-1-based medication regurgitated or aspirated, compared with about 1 in every 1,000 people who hadn’t used one. This is where the ‘11 times higher’ figure comes from.
However, the researchers couldn’t account for obesity, diabetes, reflux, or the type of surgery, which can also affect aspiration risk. This means the study can’t prove the medications caused the increased risk.
The 11-times-higher figure combines regurgitation and aspiration, but all 19 cases among medication users involved regurgitation:
- All 19 events among medication users involved regurgitation, where stomach contents came back up into the mouth
- Two of the 1,348 medication users experienced aspiration, where material entered the airway or lungs, equal to about 1 in 674
- Aspiration occurred in 16 of the 45,691 non-users, equal to about 1 in 2,856
- Ten of the 19 events among medication users happened during emergence, the period when someone is waking from anaesthesia
The study didn’t find an 11-fold increase in aspiration. Too few aspiration events made it difficult to estimate the medicine-specific risk.
No medication user with an event developed pneumonia, needed immediate reintubation or critical-care admission, or died.
However, event severity wasn’t recorded for 17 of the 19 cases, so the absence of documented complications shouldn’t be treated as proof that every event was harmless1.
How strong is the evidence?
GLIMPSE included 47,039 people having anaesthetic care at 119 UK hospitals, making it the largest prospective UK study in this area. Because clinicians recorded events as procedures happened, it provides stronger evidence of a link with regurgitation than earlier studies based on medical records.
It was still an observational study, so it can show an association but can’t prove that Wegovy or Mounjaro caused the events.
The researchers didn’t collect the same level of detail for most non-users. They couldn’t adjust the comparison for obesity, diabetes, reflux, the type and urgency of surgery, or other aspiration risks.
Anaesthetists also knew who was taking the medication. Greater vigilance in that group could make regurgitation more likely to be noticed and reported.
More than 80% of medication users who had general anaesthesia received a tracheal tube to protect the airway. This may have stopped some regurgitation from progressing to aspiration, so the findings partly reflect the precautions used.
Thirty per cent of medication users had been told to pause treatment, usually for 8 to 14 days. GLIMPSE wasn’t designed to compare people who stopped with those who continued, so it can’t tell us whether that pause in treatment helped1.
A 2025 systematic review included 28 observational studies and analysed retained stomach contents and aspiration separately.
Across 18 studies, people taking GLP-1 medications had almost six times the odds of food or fluid remaining in their stomach despite fasting.2
Nine studies, involving 185,414 people and 471 cases of aspiration, compared aspiration between medication users and non-users. When these results were combined, aspiration was no more common among people taking GLP-1 medications.2
Most studies relied on existing medical records, so the review found no clear increase in aspiration, rather than proving no increased risk.
Taken together, the studies show that people taking GLP-1 medications are more likely to have food left in their stomach after fasting and to regurgitate during anaesthetic care.
Anaesthetists need to know whether a patient of theirs is on GLP-1 medication so they can decide whether to check the stomach with an ultrasound or use a breathing tube to protect the airway.
Still, no study has shown that stopping Wegovy or Mounjaro for a set number of weeks reduces aspiration, so the evidence doesn’t support a routine pause in treatment for everyone.
Why does UK guidance still say to continue treatment?
The evidence shows that these medications can leave more content in the stomach. It still doesn’t show whether stopping the medication, fasting longer, or following a liquid-only diet reduces aspiration.
Wegovy and Mounjaro slow how quickly our stomach empties. This can leave food or drink in the stomach even after someone follows the usual pre-operative instructions: typically no food for six hours and no clear fluids for two hours.
Seven days after the last injection, about half of the semaglutide from Wegovy and more than a third of the tirzepatide from Mounjaro is still in the body.3
It takes roughly five weeks for Wegovy and four weeks for Mounjaro to mostly leave the body. But no study has shown that stopping for this long returns stomach emptying to normal or reduces aspiration.
Stopping the medication also has consequences. For people living with type 2 diabetes, it can worsen blood glucose control around surgery. Longer interruptions can disrupt treatment and may change the dose at which it’s safe to restart.
The UK consensus therefore recommends continuing treatment and managing the risk around the procedure. This may include:
- Choosing local or regional anaesthesia where suitable
- Checking the stomach with ultrasound where the equipment and expertise are available
- Using positioning and airway techniques that reduce the chance of stomach contents reaching the lungs
- Planning carefully for removal of the breathing tube and emergence from anaesthesia
In GLIMPSE, more than half of the regurgitation or aspiration cases among people taking GLP-1 medications happened during emergence, the period when someone is waking from anaesthesia and their breathing tube may be removed.
This finding gives UK guideline groups a reason to review how anaesthetic teams protect the airway as someone wakes up. But GLIMPSE doesn’t show that Wegovy or Mounjaro should be stopped before surgery, or how long they would need to be stopped to reduce aspiration.
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Why are hospitals giving different advice?
Current national UK guidance tells people to continue Wegovy or Mounjaro before surgery. Some NHS trusts tell people to stop for between one and five weeks.
The advice differs because no study has compared continuing treatment with stopping for different lengths of time. Clinicians therefore don’t know whether stopping reduces aspiration or how long someone would need to stop for.
| Source |
What it advises |
| UK multidisciplinary consensus, 2025 |
Continue taking the medication. Tell the anaesthetic team your dose, any recent dose changes, and digestive symptoms so they can decide whether measures such as a stomach ultrasound or a breathing tube are needed.3 |
| MHRA safety advice, 2025 |
Take the medication as prescribed and don’t stop without speaking to your doctor. The MHRA found too little evidence to recommend a fixed number of days without treatment, longer fasting, or a routine test to check whether the stomach is empty.4 |
| University Hospitals Sussex, 2026 |
Most people receiving cancer treatment are advised to stop weight-loss injections seven days before an anaesthetic.5 |
| NHS Lanarkshire, 2025 |
For people taking these medications for weight management, guidance allows stopping Mounjaro four weeks before surgery or Wegovy five weeks before. It also says surgery shouldn’t be cancelled solely because someone continued treatment.6 |
Seven days isn’t long enough for either medication to leave the body. Four or five weeks is roughly how long they take to mostly leave, but no trial has shown that waiting this long prevents aspiration.
Contact the hospital’s pre-assessment team before the procedure. Tell them which medication you take, the dose, when you last took it, why you take it, and whether you have nausea, vomiting, reflux, or abdominal fullness.
Ask whether you should take your next dose, when you need to stop eating and drinking, and when to restart if they tell you to stop.
If your prescriber gives different advice, ask the prescriber and anaesthetic team to agree on one plan before the procedure.
What should you do before a planned procedure?
Tell the team as early as possible, rather than waiting until the day of the procedure.
- Give them the medication name, dose, injection day, date of your last dose, why you take it, and where it was prescribed
- Report nausea, vomiting, abdominal pain or fullness, severe reflux, constipation, or a diagnosis of gastroparesis, where the stomach empties unusually slowly
- Tell them if you’ve recently started treatment or increased the dose, because digestive side effects are often stronger during these periods
- Ask whether the procedure involves general anaesthesia, deep sedation, lighter sedation, or local anaesthetic only
- Follow the team’s fasting and medication plan exactly. Don’t fast for longer or switch to a liquid diet unless they ask you to.
- If you’re told to pause treatment, ask when and at what dose to restart, particularly if the break will last several weeks and speak to your prescriber immediately
Private prescriptions don’t always appear in NHS medication records. In GLIMPSE, more than 40% of medication users received their prescription from somewhere other than a GP or hospital specialist1.
Our guide to using Mounjaro before weight-loss surgery covers the wider evidence for treatment before bariatric surgery. Your surgical team still needs to provide the anaesthetic plan.
What happens if surgery is urgent?
Don’t delay urgent care because you’ve recently taken Wegovy or Mounjaro.
Tell the team your dose, last injection date, reason for treatment, and whether you have nausea, vomiting, reflux, or abdominal fullness.
The anaesthetic team can treat you as someone who may have a full stomach and adapt the procedure and airway plan. Taking the medication isn’t, by itself, a reason to avoid necessary emergency surgery.
Frequently asked questions
How long before surgery should I stop Wegovy?
Current UK multidisciplinary guidance doesn’t recommend a routine pause in treatment, so you should continue Wegovy unless your anaesthetic team gives you a different instruction3.
Local policies vary. A one-week pause in treatment hasn’t been shown to prevent aspiration, and Wegovy remains active in the body for considerably longer than a week3.
How long before surgery should I stop Mounjaro?
You shouldn’t routinely stop Mounjaro before surgery under current UK multidisciplinary guidance3. Follow your anaesthetic team’s specific instructions if they advise a pause in treatment.
If you take Mounjaro for type 2 diabetes, the team also needs a plan for your blood glucose and other diabetes medication while it is withheld3.
Can I have a local anaesthetic while taking Wegovy or Mounjaro?
Usually, yes. The MHRA warning is specifically about general anaesthesia and deep sedation, where the reflexes that protect our airway are reduced4.
Still tell the team because some procedures combine local anaesthetic with sedation or may need to change to a different anaesthetic.
Does the advice apply to endoscopy or sedation?
It applies directly to deep sedation and to endoscopies performed under general anaesthesia. With lighter sedation, the risk depends on how deeply sedated you’ll be, the procedure, your symptoms, and the airway plan.
Follow the endoscopy unit’s fasting, bowel-preparation, and medication instructions.
Will my surgery be cancelled if I took my injection?
A recent injection doesn’t automatically mean your surgery will be cancelled. The anaesthetist may proceed with extra precautions, change the anaesthetic, delay the procedure, or use an ultrasound scan to check the stomach if it is available.
Whether surgery goes ahead as planned depends on how urgent it is, whether you’ve recently increased your dose, whether you have digestive symptoms, and the type of anaesthetic being used.
Telling the team before the day of surgery gives them time to arrange a stomach ultrasound, use a breathing tube to protect your airway, or reschedule the procedure if necessary.
Should I fast for longer or have clear liquids for 24 hours?
Don’t change the fasting plan yourself. Longer fasting doesn’t guarantee an empty stomach in people taking GLP-1 medication, and the UK consensus recommends standard fasting protocols unless the clinical team makes an individual change3.
What if my injection is due just before surgery?
Take it on the usual day unless your pre-operative or anaesthetic team has told you not to. If you can’t get an answer, contact the hospital’s pre-assessment service rather than changing it yourself.
When can I restart Wegovy or Mounjaro after surgery?
If you continued treatment, you don’t need to restart. If the team told you to pause, ask for a written restart date and dose before you leave the hospital.
When you restart and which dose you use depends on how many injections you missed, whether you’re eating and drinking normally, whether you still have digestive symptoms, and whether you take the medication for diabetes.
If you’ve missed several weekly injections, don’t restart at your previous dose without speaking to your prescriber. You may need to restart at a lower dose to reduce digestive side effects.
Do I need to mention a private prescription?
Yes. Private Wegovy and Mounjaro prescriptions may not appear in your NHS record, so tell the pre-operative team and anaesthetist directly4.
Bring the pen, packaging, prescription record, or a clear photo if you’re unsure of the dose.
Take home message
Current UK multidisciplinary guidance recommends continuing Wegovy and Mounjaro before elective surgery.
Your anaesthetic team may give different instructions if you’ve recently increased your dose, have nausea, vomiting, reflux or abdominal fullness, or have another condition that slows stomach emptying. Don’t stop the medication without speaking to them first.3
In GLIMPSE, 19 of 1,348 people who had used a GLP-1 medication regurgitated or aspirated, compared with 57 of 45,691 people who hadn’t used one. This is where the study’s ‘11 times higher’ figure comes from.
All 19 cases among medication users involved regurgitation, where stomach contents came back up. Only two also involved aspiration, where the contents entered the airway. The 11-times-higher figure therefore mainly describes more regurgitation, not more aspiration.1
More than half of the cases among medication users happened as people woke from anaesthesia. Telling the anaesthetic team about the medication beforehand gives them time to decide whether to check the stomach with an ultrasound or use a breathing tube to protect the airway.
GLIMPSE didn’t compare people who stopped Wegovy or Mounjaro with people who continued. It therefore can’t tell us whether stopping for one week, two weeks, or longer prevents aspiration.
Before the procedure, tell the team which medication you take, the dose, when you last took it, why you take it, where it was prescribed, and whether you have digestive symptoms.
Follow their written instructions for taking the medication, fasting, and restarting treatment, even if they differ from national guidance.
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