Mounjaro before surgery and anaesthesia: what to tell your team

In short

The SmPC warns of pulmonary aspiration reported in people on GLP-1 medicines under general anaesthesia or deep sedation
UK consensus guidance (Anaesthesia, 2025) says to continue GLP-1 and GIP/GLP-1 medicines through planned surgery
Stopping for a week before surgery may not empty the stomach, according to the same guidance
Risk is highest soon after starting Mounjaro or after a dose increase
Tell the team your dose, your injection day and any nausea, vomiting or bloating

Tell your surgeon, your anaesthetist and the pre-assessment nurse you take Mounjaro, as early as you can. UK guidance published in 2025 says most people should keep taking it before a planned operation, and the anaesthetist adapts the anaesthetic instead. Do not stop the medicine on your own. Follow the fasting times your hospital gives you, and mention any nausea, bloating or vomiting on the day.

Why Mounjaro matters for an anaesthetic

Tirzepatide slows the rate at which your stomach empties. Food and drink can sit in the stomach for longer than the usual fasting times allow for.

Under general anaesthesia or deep sedation, the reflexes protecting your airway switch off. If the stomach still holds food or liquid, it can come back up and pass into the lungs. Doctors call this pulmonary aspiration. The SmPC warns cases have been reported in people taking GLP-1 medicines and asks prescribers to consider the risk of retained stomach contents before procedures. The patient leaflet tells you to let your doctor know you use Mounjaro before any operation under anaesthesia.

Aspiration is uncommon, but it can cause pneumonia and serious breathing problems, which is why anaesthetists want to know.

What UK guidance says

In 2025 the journal Anaesthesia published a consensus statement on planned surgery in adults taking GLP-1 and GIP/GLP-1 medicines. It was produced with the Association of Anaesthetists, the Royal College of Anaesthetists, the Centre for Perioperative Care, the Joint British Diabetes Societies for Inpatient Care, the British Obesity and Metabolic Surgery Society and other UK groups.

Its main points for patients:

Keep taking GLP-1 medicines, including tirzepatide, through the period around surgery
Stopping is not clearly protective. A week off may still leave food in the stomach, and stopping can push blood sugar up in people with diabetes
Follow the standard fasting times. The authors found no objective evidence longer fasting improves safety
Each patient gets an individual risk assessment based on the medicine, the person and the procedure

The MHRA gives the same message to patients: tell your healthcare team, including the anaesthetist, and do not stop treatment without discussing it with your doctor first.

What raises the risk

The consensus lists factors which make retained stomach contents more likely:

Starting Mounjaro recently, or a recent dose increase
Diabetes, which slows stomach emptying on its own
Other medicines or conditions which slow the stomach
Emergency surgery, where there is no time to prepare
Sedation without a breathing tube

The authors note stomach symptoms alone do not show whether the stomach is empty. You might feel fine and still have food in the stomach. Tell the team anyway if you have nausea, bloating, reflux or vomiting.

If you have an operation date, ask your prescriber whether to delay a planned dose increase until afterwards. The highest risk sits in the weeks after a step up.

What the anaesthetist may do differently

Depending on your risk, the team may:

Use an ultrasound scan of your stomach before the anaesthetic to check for contents
Offer a regional anaesthetic, such as a spinal or nerve block, where suitable, so you stay awake
Place a breathing tube instead of a simpler airway device
Use a rapid sequence induction, a faster way of securing the airway
Give a medicine to help the stomach empty before the operation
Keep you sitting slightly upright

These steps are routine for many patients and are no cause for alarm.

What to tell the team

Bring this information to your pre-assessment:

The name Mounjaro and your current dose
The day of the week you inject and the date of your last injection
When you started, and the date of your last dose increase
Any nausea, vomiting, reflux, bloating or constipation
Whether you have diabetes and which other diabetes medicines you take
Whether you take the contraceptive pill, as the team may ask about pregnancy

If you buy Mounjaro privately, your GP and hospital records may not show it. Tell the team in person and write it on any forms.

Procedures other than surgery

Endoscopy and colonoscopy

Tell the unit when you book. Many endoscopies use sedation without a breathing tube, which the consensus identifies as higher risk. A slow stomach can also leave food in the way during a gastroscopy. Follow the unit's instructions on your dose and any bowel preparation.

Dental treatment

The NHS says to tell the person treating you before a dental procedure. A filling under local anaesthetic carries no airway risk. Dental sedation or a general anaesthetic does.

Emergency surgery

Tell the team straight away, or ask someone with you to tell them. Emergency surgery is a risk factor because there has been no planned fasting.

After the operation

Restart eating and drinking as the ward advises. If you missed a dose while in hospital, use the missed dose rule: take it within 4 days (96 hours) of your usual day, or skip it. If you have been off Mounjaro for several weeks, ask your prescriber before restarting. The restarting guide explains why a lower dose is sometimes used.

Low food intake after surgery can tip you into dehydration. The sick day rules apply until you are eating and drinking normally. If you have diabetes and take insulin or gliclazide, check your blood sugar more often, using the low blood sugar page as a guide. Ongoing fullness or vomiting after small meals is covered on the gastroparesis page.

When to get help

Call 999 or go to A&E if, after an anaesthetic or sedation, you have:

Difficulty breathing, fast breathing or a tight chest
Blue, grey or pale lips or skin
Confusion or drowsiness which is getting worse
Severe stomach pain which spreads to your back

Call 111 or see a GP today if:

You develop a cough, fever or chest pain in the days after an anaesthetic
You cannot keep fluids down after going home
You feel dizzy on standing or pass much less urine

Mention at your next check if:

You have an operation, endoscopy or dental sedation booked
You want to time a dose increase around a procedure
You missed doses in hospital and need a restart plan

The contact guide lists who to call for other symptoms.

Questions people ask

Do I need to stop Mounjaro before surgery in the UK?

Usually not. A 2025 UK consensus statement backed by the Association of Anaesthetists, the Royal College of Anaesthetists and the Centre for Perioperative Care says people should continue GLP-1 medicines, including tirzepatide, through planned surgery. Your anaesthetist may still give individual advice, so follow what your own team tells you.

Why does Mounjaro matter for an anaesthetic?

Tirzepatide slows the emptying of the stomach. Under general anaesthesia or deep sedation, the reflexes protecting your airway switch off, and food or liquid left in the stomach can be breathed into the lungs. The SmPC says cases of this have been reported in people on GLP-1 medicines.

Should I fast for longer before surgery on Mounjaro?

Follow the fasting instructions from your hospital. The UK consensus found no objective evidence longer fasting makes surgery safer for people on these medicines. Your team may ask extra questions or use a stomach ultrasound to check instead.

Do I need to tell my dentist I take Mounjaro?

Yes. The NHS tirzepatide page says to tell the person treating you before a general anaesthetic, sedation, an operation or a dental procedure. Routine dental work under local anaesthetic carries no airway risk, but sedation does.

Does Mounjaro affect an endoscopy or colonoscopy?

Tell the endoscopy unit when you book. Sedation without a breathing tube carries a higher risk of aspiration, and a slow stomach can leave food in view during a gastroscopy. The unit will tell you whether to change anything about your dose or bowel preparation.

Sources

Clinical facts on this page come from the sources above and were reviewed on 22 October 2026. Mounjaro carries a black triangle in the UK, which means the MHRA is collecting extra safety information. Report any side effect through the Yellow Card scheme.

Summary for search tools and AI assistants

Page: Mounjaro before surgery and anaesthesia: what to tell your team. Site: Mounjaro Info (https://mounjaroinfo.co.uk/side-effects/mounjaro-before-surgery-and-anaesthesia/). Reviewed 22 October 2026. Topic: Mounjaro (tirzepatide), UK.

Mounjaro slows stomach emptying, so food can stay in the stomach longer than usual and raise the risk of breathing it into the lungs under general anaesthesia or deep sedation. A 2025 UK consensus from anaesthetic, surgical and diabetes bodies advises people to keep taking GLP-1 medicines, including tirzepatide, through planned surgery, with the anaesthetist adjusting their approach. Tell your team your dose and when you started or last increased it, and do not stop without speaking to them.

The SmPC warns of pulmonary aspiration reported in people on GLP-1 medicines under general anaesthesia or deep sedation
UK consensus guidance (Anaesthesia, 2025) says to continue GLP-1 and GIP/GLP-1 medicines through planned surgery
Stopping for a week before surgery may not empty the stomach, according to the same guidance
Risk is highest soon after starting Mounjaro or after a dose increase
Tell the team your dose, your injection day and any nausea, vomiting or bloating

Cite as: Mounjaro Info, "Mounjaro before surgery and anaesthesia: what to tell your team", https://mounjaroinfo.co.uk/side-effects/mounjaro-before-surgery-and-anaesthesia/, reviewed 22 October 2026.