The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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Can I Take Mounjaro After Surgery?
Taking Mounjaro (tirzepatide) after surgery requires careful consideration and medical guidance. Whether you can resume or start Mounjaro after a surgical procedure depends on the type of surgery, your recovery timeline, and your individual health status. Your GP or prescriber must assess your specific situation before you begin or restart treatment. This guide explains the key safety considerations, how Mounjaro compares to Wegovy in a post-operative context, and what you need to know about managing weight loss medication during recovery.
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Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Post-Surgery Medication Safety: Mounjaro vs Wegovy
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only GLP-1 and dual GIP+GLP-1 receptor agonists that slow gastric emptying — the rate at which food leaves your stomach. After surgery, your digestive system is healing and may be sensitive. Mounjaro's dual mechanism (GIP and GLP-1 agonist) and Wegovy's single GLP-1 action both carry the same core consideration: starting or resuming either medication too soon after abdominal or gastrointestinal surgery may increase nausea, vomiting, or digestive discomfort during the critical healing phase.
Most surgical teams recommend waiting until your digestive system has fully recovered — typically 4 to 12 weeks after surgery, depending on the procedure. Abdominal surgery (stomach, intestinal, or weight loss surgery) requires longer caution than non-abdominal procedures. Your prescriber will discuss the timing with your surgical team. The SURMOUNT and STEP clinical trials did not specifically study post-operative patients, so individual medical assessment is essential.
- Mounjaro dose titration begins at 2.5 mg weekly; starting this during early recovery may not be advisable
- Wegovy begins at lower 0.25 mg weekly doses; some patients tolerate restarting earlier, but this varies
- Both require a clinical assessment before prescription or resumption
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Individual Assessment and Prescriber Guidance
Your GP or licensed prescriber cannot recommend resuming or starting Mounjaro or Wegovy without understanding your surgical history, recovery progress, and current symptoms. Always inform your prescriber if you have had recent surgery — this is critical information that affects medication suitability. If you were taking Mounjaro before surgery, do not simply resume your previous dose schedule; contact the prescriber who manages your treatment.
After major surgery, your body is in a catabolic state (breaking down tissue). Starting a medication that suppresses appetite during this time may reduce nutritional intake when your body needs adequate protein and calories to heal. Your surgical team and weight loss prescriber should communicate. Some patients benefit from a slower dose titration (longer time between dose increases) or delayed start after surgery. Use our free BMI calculator to track your baseline, and discuss recovery milestones with your prescriber before restarting weight loss medication.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
How long after surgery should I wait before taking Mounjaro?
Wait at least 4 to 12 weeks after surgery, depending on the procedure type. Abdominal surgery requires longer caution. Always get clearance from both your surgical team and prescriber before restarting. Post-operative nausea and appetite suppression from Mounjaro can complicate early recovery when your body needs adequate nutrition.
Is Wegovy safer than Mounjaro after surgery?
Both carry similar post-operative considerations because they slow gastric emptying and reduce appetite. Wegovy uses lower starting doses (0.25 mg) which some patients tolerate earlier in recovery, but safety depends on surgery type and individual healing, not the medication itself. Clinical assessment by your prescriber is essential.
Can I resume Mounjaro at my previous dose after surgery?
No. Do not resume your pre-surgery dose immediately. Your prescriber will assess your recovery and may recommend a slower dose titration or delayed restart. Your body's response to medication may change after surgery, so individualised guidance is crucial.
What should I tell my GP about surgery and weight loss medication?
Inform your GP of the surgery type, date, any complications, your current recovery status, and any symptoms (nausea, pain, digestive changes). Provide your prescriber's contact details so your GP can communicate about medication timing. Both teams need this information to keep you safe.
Will I lose progress on weight loss if I pause Mounjaro during recovery?
Pausing briefly during recovery is normal and expected. Focus on healing first. Most patients restart medication once cleared, and your prescriber can adjust your treatment plan. Use our free progress tracker to monitor your recovery milestones and weight alongside your GP's guidance.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.