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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Restarting Mounjaro After Surgery: NHS UK Guidance
If you've had surgery and paused your Mounjaro treatment, you'll need guidance on when and how to safely restart. In the UK, restarting Mounjaro after surgery requires discussion with your prescriber or GP, as the timing depends on the type of surgery, your recovery, and whether you can manage oral medications safely. This guide covers NHS guidance, what to expect, and practical steps for resuming your tirzepatide injections post-surgery.
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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.
When to Restart Mounjaro After Surgery
The timing for restarting Mounjaro depends on several factors specific to your surgery and recovery. Most minor surgeries allow resumption within 1–2 weeks once you can manage food and oral medications normally. For major abdominal or gastrointestinal surgery, your prescriber may recommend waiting 2–4 weeks or longer.
- Minor surgery (e.g. dental, skin): Usually restart after 1–2 weeks if recovering well
- Major surgery (e.g. abdominal, bariatric): May need to wait 3–6 weeks; discuss with your surgical team
- Gastrointestinal surgery: Delayed restart common due to altered digestion — your prescriber will advise
Your prescriber will also consider whether your body can tolerate the medication alongside post-surgery medications. Always contact your GP or the team that prescribed Mounjaro before restarting — do not resume without guidance.
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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.
Practical Steps for Restarting Treatment
Once cleared to restart, you may resume at your current dose rather than starting from 2.5 mg again. Contact your prescriber 1–2 weeks before your expected restart date to arrange a new prescription and KwikPen supply. Confirm you have storage space in your fridge (2–8°C) and that you're managing post-surgery pain and nausea well — both can be exacerbated by Mounjaro initially.
If you experienced nausea or stomach discomfort before surgery, take anti-sickness medication 30 minutes before your first injection after the break. Keep a food and symptom diary for the first 2 weeks post-restart to monitor how your body responds. If you've had significant time off Mounjaro (over 8 weeks), discuss whether dose re-titration makes sense for your individual situation.
- 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.
Can I take Mounjaro immediately after surgery?
No. You'll need to wait until you can manage food normally and your surgical team confirms you're fit to resume medications. Minor surgery typically allows restart after 1–2 weeks; major surgery may require 3–6 weeks. Always contact your prescriber for personalised timing.
Do I restart at my previous Mounjaro dose or begin again at 2.5 mg?
Most prescribers allow you to resume at your previous stable dose (e.g. 10 mg or 15 mg) rather than re-titrating from 2.5 mg, as your body is already adapted to the medication. Discuss this with your prescriber — they may adjust based on time off and your recovery.
What if I had nausea on Mounjaro before surgery — will it be worse after restarting?
Possibly, as post-surgery nausea can compound medication-related nausea. Take prescribed anti-sickness medication 30 minutes before your first injection, stay hydrated, and eat small frequent meals. If severe nausea develops, contact your GP — dose adjustment may help.
How long can I safely pause Mounjaro during surgery without losing the effect?
A pause of 1–2 weeks for minor surgery has minimal impact. Pauses of 3–4 weeks (major surgery) may slightly reduce the metabolic benefit, but restarting at your previous dose typically restores effect within 4–6 weeks as your body re-adapts.
Should I inform my surgical team that I take Mounjaro before my operation?
Yes, absolutely. Tell your anaesthetist and surgical team about Mounjaro, when you last injected, and any side effects (especially nausea or stomach issues). They may adjust anaesthesia or post-op medication accordingly to manage potential interactions safely.
Ready to take control of your weight loss journey?
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