Mounjaro (tirzepatide) is a GLP-1 and GIP receptor agonist used for type 2 diabetes management in the UK. Its effect of delaying gastric emptying raises important considerations for patients undergoing surgery, as this may increase aspiration risk during anaesthesia. UK guidance now emphasises individualised risk assessment rather than routine cessation. The decision to pause Mounjaro before surgery depends on your specific procedure, risk factors, and anaesthetist's evaluation. This article explains current UK recommendations, timeframes for pausing treatment, blood glucose management strategies, and when to safely restart Mounjaro post-operatively.

Why Mounjaro May Need to Be Paused Before Surgery

Mounjaro (tirzepatide) is a glucagon-like peptide-1 (GLP-1) receptor agonist and glucose-dependent insulinotropic polypeptide (GIP) receptor agonist used primarily for type 2 diabetes management in the UK. One of its key pharmacological effects is delayed gastric emptying, which slows the movement of food from the stomach into the small intestine. Whilst this mechanism contributes to improved glycaemic control and satiety, it may pose risks in the perioperative setting that need individual assessment.

When undergoing surgery requiring general anaesthesia or procedural sedation, patients must typically fast to ensure the stomach is empty. This precaution reduces the risk of aspiration—a complication where stomach contents are regurgitated and inhaled into the lungs during anaesthesia. Because Mounjaro delays gastric emptying, food may remain in the stomach longer than expected, even after standard fasting periods, potentially increasing aspiration risk.

UK anaesthetic practice increasingly favours individualised risk assessment rather than universal cessation of GLP-1 receptor agonists. The Centre for Perioperative Care (CPOC) and UK anaesthetic bodies recommend discussing Mounjaro use with your anaesthetist during pre-operative assessment. This allows them to evaluate your specific risk factors, such as whether you're in the dose-escalation phase, have significant gastrointestinal symptoms, or known gastroparesis.

Surgical teams must be informed of all medications, including Mounjaro, to allow appropriate risk assessment and fasting modifications. In some cases, particularly for higher-risk patients, your anaesthetist may recommend temporarily pausing Mounjaro before your procedure. This approach ensures your safety whilst avoiding unnecessary medication disruption for lower-risk situations.

Recommended Timeframe to Pause Mounjaro Before Surgery

The appropriate approach for Mounjaro before surgery depends on individual assessment and local hospital policies. Tirzepatide has a half-life of approximately five days, meaning it takes roughly this time for half the drug to be eliminated from the body. This pharmacokinetic profile informs perioperative planning, but recommendations vary based on individual risk factors.

Many UK hospitals and anaesthetists may recommend pausing Mounjaro for a period before elective surgery requiring general anaesthesia or deep sedation, particularly for patients with additional risk factors. The exact timing should be determined through discussion with your anaesthetist and surgical team, following your hospital's specific protocols.

For procedures involving moderate sedation or local anaesthesia only, where aspiration risk is substantially lower, continuing Mounjaro may be appropriate. This decision should be made collaboratively between you, your surgeon, and anaesthetist, taking into account your diabetes control, surgical complexity, and individual risk factors.

It is important to note that Mounjaro is administered as a once-weekly subcutaneous injection. If your healthcare team advises pausing treatment, they will provide specific guidance about which dose to skip. For example, if your anaesthetist recommends pausing treatment and surgery is planned for a Friday, they may advise not administering your usual injection the week before.

For emergency surgery, there is insufficient time for planned drug adjustment. In such cases, make sure to inform the emergency medical team about your Mounjaro use so they can implement appropriate precautions. Your anaesthetist may use additional risk-mitigation strategies, such as considering you at higher risk for gastric contents and adapting their approach accordingly.

Risks of Continuing Mounjaro Too Close to Surgery

Continuing Mounjaro close to surgery may increase certain perioperative risks in some patients. The primary concern relates to pulmonary aspiration, which occurs when gastric contents enter the respiratory tract during induction of anaesthesia, airway manipulation, or emergence from sedation. While the absolute risk appears low based on available evidence, case reports and observational studies have raised concerns that warrant consideration.

Some studies examining GLP-1 receptor agonists have documented cases of retained gastric contents despite adherence to standard nil-by-mouth protocols. Patients taking these medications have been found to have gastric residue even after fasting for 12–14 hours, exceeding normal expectations. This altered gastric emptying may make traditional fasting guidelines less reliable for some patients.

In some cases, anaesthetists may postpone elective surgery if they identify concerns during preoperative assessment. This is done to ensure patient safety but can cause inconvenience and anxiety. Additionally, some patients may experience nausea and vomiting during the perioperative period due to Mounjaro's effects, potentially complicating post-anaesthetic recovery.

There is also consideration of blood glucose management if Mounjaro is paused alongside perioperative fasting. While tirzepatide's glucose-dependent mechanism makes severe hypoglycaemia less likely than with insulin or sulphonylureas, the combination of medication changes, fasting, and surgical stress can create unpredictable glycaemic fluctuations. This is particularly relevant for patients taking additional glucose-lowering medications.

If you have concerns about the risks or benefits of continuing or pausing Mounjaro before your procedure, discuss these with your anaesthetist during your pre-operative assessment. They can provide personalised advice based on your medical history, the specific procedure, and current UK guidance.

Managing Blood Sugar During the Mounjaro Pause

If your healthcare team recommends temporarily pausing Mounjaro, you may have concerns about glycaemic control, particularly if you have type 2 diabetes. A relatively short withholding period means most patients can maintain acceptable blood sugar levels with appropriate monitoring and interim strategies.

For patients using Mounjaro solely for type 2 diabetes management, discuss with your GP or diabetes team whether you need alternative glucose-lowering strategies during the brief pause. For those with well-controlled diabetes, simple monitoring may be sufficient without medication changes.

Monitoring strategies during a Mounjaro pause should include:

• Increased blood glucose testing—checking levels at least twice daily (fasting and pre-evening meal) or as advised by your diabetes team

• Maintaining a glucose diary to identify patterns and guide any necessary interventions

• Recognising hyperglycaemia symptoms such as increased thirst, frequent urination, fatigue, or blurred vision

Some patients may require temporary medication adjustments during the Mounjaro-free period. It's important to note that SGLT2 inhibitors (medications like empagliflozin, dapagliflozin, canagliflozin) are typically stopped 3 days before surgery in the UK due to the risk of euglycaemic diabetic ketoacidosis. Do not start these as temporary alternatives. Metformin is often continued until the day before surgery for many procedures, but follow your hospital's specific guidance.

Dietary modifications can help maintain glycaemic stability, including consistent carbohydrate intake, avoiding concentrated sugars, and maintaining regular meal timing. Be aware that stress about upcoming surgery may itself affect blood glucose levels. Contact your diabetes care team or GP if you experience concerning glucose readings (typically sustained levels above 12-15 mmol/L or below 4 mmol/L) for guidance.

If you have complex diabetes or are concerned about managing without Mounjaro, ask for a referral to the hospital diabetes team before your procedure. They can provide a personalised perioperative diabetes management plan.

When to Restart Mounjaro After Surgery

Resuming Mounjaro after surgery requires consideration of your recovery status, oral intake tolerance, and surgical outcomes. There is no universal timeline, as the appropriate restart point varies depending on the procedure type, post-operative course, and individual factors. Generally, Mounjaro should only be restarted once you have fully recovered from anaesthesia, are tolerating normal oral intake without nausea or vomiting, and have received clearance from your surgical team.

For minor procedures with uncomplicated recovery, you may be able to resume Mounjaro once you return to your regular eating pattern—often within a few days post-operatively. However, for major abdominal surgery, gastrointestinal procedures, or operations with prolonged recovery, a longer delay may be necessary. Your surgeon will advise when it's appropriate to restart, which might be once specific recovery milestones are achieved, such as return of normal bowel function, removal of drains, or transition to solid foods.

You should be particularly cautious about restarting Mounjaro if you experience post-operative nausea, vomiting, or delayed gastric emptying, as the medication may exacerbate these symptoms. Similarly, if your post-operative pain management includes opioid painkillers—which themselves slow gastric motility—delaying Mounjaro restart may be advisable to avoid compounding gastrointestinal side effects.

When restarting Mounjaro:

• Confirm with your surgical team that you may resume your regular medications

• Ensure you're tolerating adequate oral fluid and food intake for at least 24 hours

• Administer your next dose according to your usual injection schedule

• Monitor for gastrointestinal side effects, which may be more pronounced after a medication break

If you've had a longer break from Mounjaro, your doctor may advise restarting at a lower dose and gradually increasing to your previous dose to minimise side effects. Always contact your GP or diabetes team if uncertain about restart timing, particularly if your recovery is complicated or if blood glucose control has been challenging during the Mounjaro pause.

Discussing Your Mounjaro Plan with Your Surgical Team

Open communication with healthcare professionals is essential for safe perioperative management of Mounjaro therapy. You should proactively disclose your use of tirzepatide during all pre-operative assessments, as surgical teams may not automatically identify this medication or recognise its implications for anaesthesia. This conversation should occur as early as possible—ideally when surgery is first scheduled—to allow adequate planning time.

During your pre-operative assessment, provide comprehensive medication information, including:

• The exact medication name (Mounjaro/tirzepatide), dose, and frequency

• The date of your most recent injection

• The indication for use (type 2 diabetes)

• Any other glucose-lowering medications or insulin therapy

• History of gastrointestinal symptoms, gastroparesis, or previous aspiration events

The anaesthetist plays a crucial role in determining appropriate fasting protocols and whether Mounjaro should be paused. They will assess your individual risk factors and provide personalised recommendations. You should feel empowered to ask questions about your specific plan, including whether you need to pause Mounjaro before surgery, what to expect regarding blood sugar management, and when restart is appropriate.

The diabetes care team—including GPs, practice nurses, diabetes specialist nurses, or hospital diabetes specialists—should also be involved in perioperative planning. They can provide guidance on interim glucose management and monitoring advice during any Mounjaro pause. Many NHS hospitals offer dedicated perioperative diabetes support for complex cases.

Key questions to discuss with your surgical team include:

• Should I pause Mounjaro before surgery, and if so, when should I take my last dose?

• Will I need alternative diabetes medications during any pause?

• How should I monitor my blood glucose in the days before surgery?

• When can I safely restart Mounjaro after the procedure?

• What glucose levels should prompt me to contact the team before surgery?

Never hesitate to contact your surgical team or GP if you have questions or concerns about your medication management. If you experience any side effects from Mounjaro that you believe are significant, you can report them through the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk). Collaborative planning between you, your surgical team, and diabetes specialists ensures optimal outcomes whilst minimising both surgical and glycaemic risks.

Frequently Asked Questions