Mounjaro (tirzepatide) is a GLP-1 and GIP receptor agonist used for type 2 diabetes and weight management in the UK. Its effect on gastric emptying raises important questions about perioperative safety, particularly regarding aspiration risk during anaesthesia. Current UK guidance from the Centre for Perioperative Care and anaesthetic colleges recommends a risk-stratified approach rather than routine cessation before surgery. Understanding when to stop Mounjaro before surgery—or whether continuation is appropriate—depends on individual risk factors, surgical type, and gastrointestinal symptoms. This article provides evidence-based guidance to help patients and clinicians navigate perioperative Mounjaro management safely.
Quick Answer: Current UK guidance recommends a risk-stratified approach to Mounjaro before surgery, with most patients continuing treatment using standard fasting protocols rather than routine cessation.
Mounjaro (tirzepatide) is a glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) receptor agonist licensed in the UK for the treatment of type 2 diabetes mellitus and, more recently, for weight management in adults with obesity. While highly effective for glycaemic control and weight reduction, Mounjaro has effects on gastrointestinal motility that require specific consideration in the perioperative setting.
The primary consideration relates to delayed gastric emptying. Tirzepatide slows the rate at which food and fluids leave the stomach, which is part of its therapeutic mechanism for promoting satiety and controlling blood glucose. This effect is most pronounced during dose escalation and when patients experience gastrointestinal symptoms, with some attenuation of this effect occurring with continued use at stable doses.
The presence of residual stomach contents during anaesthesia may increase the risk of pulmonary aspiration—a potentially serious complication where gastric material enters the lungs. This risk applies primarily to procedures requiring general anaesthesia or procedural sedation where airway protection may be compromised.
Additionally, perioperative management of Mounjaro requires consideration of blood glucose stability, particularly in patients with diabetes. Understanding the risk assessment approach helps patients and clinicians make informed decisions about perioperative management strategies.
UK guidance from the Centre for Perioperative Care (CPOC), Association of Anaesthetists, and Royal College of Anaesthetists recommends a risk-stratified approach rather than routine cessation of GLP-1 receptor agonists like Mounjaro before surgery.
Current UK perioperative guidance recommends a risk-stratified approach to managing Mounjaro (tirzepatide) before surgery, rather than routine discontinuation for all patients. The approach depends on individual risk factors and the type of anaesthesia planned.
For most patients, UK guidance supports continuing Mounjaro before surgery with standard fasting protocols (typically six hours for solids and two hours for clear fluids). However, certain factors increase aspiration risk and may warrant additional precautions:
Higher-risk features include:
Recent initiation or dose escalation of Mounjaro
Active gastrointestinal symptoms (nausea, vomiting, reflux)
Known gastroparesis or autonomic neuropathy
Higher maintenance doses (10 mg or 15 mg weekly)
Concurrent opioid use or chronic kidney disease
Procedures with higher aspiration risk
For higher-risk patients, management options may include:
A 24-hour clear liquid diet before surgery
Point-of-care gastric ultrasound assessment if available
Managing as a 'full stomach' with appropriate anaesthetic technique
In some cases, considering postponement if in active dose escalation with significant symptoms
For emergency or urgent surgery, stopping Mounjaro in advance is not possible. In these situations, the anaesthetic team must be informed immediately so they can implement appropriate safety measures based on risk assessment.
Patients should never adjust their Mounjaro regimen without consulting their prescribing clinician, particularly those with diabetes, as glycaemic management strategies must be considered. Your GP, diabetes specialist nurse, or consultant should provide individualised advice based on your specific circumstances, surgical procedure, and glycaemic control requirements.
Understanding the potential perioperative risks associated with Mounjaro (tirzepatide) helps inform appropriate management. The current evidence base consists primarily of case reports and observational studies, with the absolute risk of complications appearing relatively low but requiring consideration.
The main concern is pulmonary aspiration risk. When gastric contents are regurgitated and inhaled into the lungs during anaesthesia, this can cause aspiration pneumonitis—a chemical injury to lung tissue—or aspiration pneumonia if bacterial infection develops. Both conditions can lead to respiratory complications requiring additional treatment.
Some case reports have documented instances where patients taking GLP-1 receptor agonists had residual gastric contents despite following standard fasting protocols. This appears more common in patients who are:
Recently initiated on therapy or undergoing dose escalation
Experiencing active gastrointestinal symptoms
Taking higher doses of the medication
Perioperative glycaemic management is another important consideration. Without appropriate planning, patients with diabetes may experience hyperglycaemia, which can impair wound healing and increase infection risk. Conversely, if other glucose-lowering medications are not adjusted appropriately, hypoglycaemia may occur.
There is also the potential for surgical delays if risk assessment and management planning are not conducted in advance. This highlights the importance of discussing Mounjaro use during preoperative assessment.
Complete disclosure of medication use is essential for safe surgical care. The anaesthetic and surgical teams can only implement appropriate risk mitigation strategies when fully informed about your medications, including Mounjaro, and any gastrointestinal symptoms you may be experiencing.
Complete and accurate disclosure of all medications, including Mounjaro, is fundamental to safe surgical care. When attending preoperative assessment or surgical consultations, you should specifically inform the team that you are taking tirzepatide (Mounjaro).
Provide the following information:
Current dose (2.5 mg, 5 mg, 7.5 mg, 10 mg, or 15 mg weekly)
Duration of treatment (how long you have been taking it)
Date of last injection (particularly important if surgery is scheduled soon)
Indication for use (type 2 diabetes, weight management, or both)
Other diabetes medications you are taking
Any gastrointestinal symptoms (nausea, vomiting, reflux, bloating)
Any history of gastroparesis or delayed gastric emptying
Recent dose changes or escalations
The surgical and anaesthetic teams need this information to:
Assess your aspiration risk accurately
Determine appropriate management strategies
Plan anaesthetic technique and airway management strategy
Arrange perioperative glucose management if needed
Consider whether additional measures (such as a 24-hour liquid diet or gastric ultrasound) are warranted
If you are attending a pre-assessment clinic, the nursing staff will document your medications, but you should specifically mention Mounjaro and ask about any special instructions. Request written guidance on managing your diabetes during the perioperative period.
For day surgery or procedures in outpatient settings, do not assume the team is aware of your medication history. Bring a current medication list or your prescription details. If you receive a pre-procedure telephone call, mention Mounjaro explicitly.
Never withhold information about medication use. Your surgical team's priority is your safety, and they can only provide optimal care with complete information. If you are uncertain whether you have communicated this adequately, contact the surgical department or your GP for advice before your procedure date.
The decision about when to restart Mounjaro after surgery should be individualised based on the type of procedure performed, your recovery progress, and the return of normal gastrointestinal function. There is no universal protocol, but several important principles guide safe resumption.
For minor procedures with minimal tissue trauma and no gastrointestinal involvement, Mounjaro can typically be restarted once you are:
Tolerating normal oral diet and fluids without significant nausea or vomiting
Experiencing minimal gastrointestinal symptoms
Medically stable with no complications
This may be as soon as 48–72 hours post-procedure for straightforward day-case surgery. However, always confirm with your surgical team before resuming.
For major surgery, particularly abdominal operations, gastrointestinal procedures, or those with significant postoperative ileus risk, a longer delay is usually necessary. Resumption should wait until:
Bowel function has returned (passing flatus, bowel movements)
You are eating and drinking normally
Surgical drains (if present) have been removed
Your surgical team has given explicit clearance
This may take one to two weeks or longer. Premature resumption could exacerbate postoperative nausea, delay recovery of gut motility, and compromise nutritional intake during the critical healing phase.
Diabetes management during the gap period is crucial. Your diabetes team should provide a perioperative plan, which might include:
Adjustment of other oral hypoglycaemic agents
Temporary insulin regimens if required
Blood glucose monitoring with targets as recommended by UK guidance
When restarting Mounjaro after a prolonged break, some clinicians recommend resuming at a lower dose initially to minimise gastrointestinal side effects, then re-escalating according to the standard titration schedule. Discuss this approach with your prescribing clinician.
Contact your GP or diabetes specialist before taking your next dose if you are unsure about timing, experiencing ongoing postoperative symptoms, or if your surgical team has not provided clear guidance. Coordinated care between your surgical and diabetes teams ensures both safe resumption of Mounjaro and maintenance of glycaemic control during your recovery period.
No, current UK guidance recommends a risk-stratified approach rather than routine cessation. Most patients can continue Mounjaro with standard fasting protocols, though higher-risk patients may require additional precautions or temporary discontinuation based on individual assessment by the surgical and anaesthetic teams.
Higher-risk features include recent initiation or dose escalation of Mounjaro, active gastrointestinal symptoms such as nausea or vomiting, known gastroparesis, higher maintenance doses, concurrent opioid use, and procedures with inherently higher aspiration risk. Your anaesthetic team will assess these factors during preoperative evaluation.
Timing depends on procedure type and recovery. For minor procedures, resumption may be appropriate within 48–72 hours once you tolerate normal diet without significant symptoms. For major surgery, particularly abdominal procedures, wait until bowel function returns and your surgical team provides explicit clearance, typically one to two weeks or longer.
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