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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How to Avoid Pancreatitis With Mounjaro
Pancreatitis is a serious but rare side effect associated with GLP-1 and GIP/GLP-1 medications like Mounjaro (tirzepatide) and Wegovy (semaglutide). This guide explains what pancreatitis is, how to recognise warning signs, and practical steps to reduce your risk. Both medications require a prescription and clinical assessment beforehand — your prescriber will evaluate your individual pancreatitis risk as part of that process. Understanding what to watch for helps you use these medications safely.
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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.
Clinical Evidence and Mechanism Differences
Pancreatitis risk is low but documented with both Mounjaro and Wegovy. In the SURMOUNT-1 clinical trial for Mounjaro (tirzepatide), pancreatitis was reported in less than 0.5% of participants. The STEP-1 trial for Wegovy (semaglutide) showed similar rare incidence. Both medications work on the pancreas indirectly — Mounjaro uses a dual GIP and GLP-1 mechanism, whilst Wegovy uses GLP-1 only. This mechanism difference does not mean one is safer than the other; pancreatitis risk appears comparable between them. The condition typically occurs within the first few months of treatment or after a dose increase. Your prescriber will assess your personal pancreatitis risk based on your medical history, previous pancreatic problems, or gallbladder disease before prescribing either medication.
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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.
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Warning Signs and Prevention Strategies
Seek urgent medical attention if you experience severe, persistent stomach pain spreading to your back — this is the primary warning sign of pancreatitis. Other symptoms include nausea, vomiting, and abdominal tenderness. To reduce your risk: inform your prescriber of any history of pancreatitis, gallstones, or gallbladder disease before starting; avoid sudden, large dose increases (dose titration should be gradual — typically 4 weeks per increment); stay hydrated and follow dietary guidance; and report any unusual stomach pain immediately to your GP. If pancreatitis is suspected, stop the medication and seek emergency care. Both medications should not be used if you have a personal or family history of medullary thyroid cancer or multiple endocrine neoplasia type 2.
- 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.
What exactly is pancreatitis and why does it happen with Mounjaro?
Pancreatitis is inflammation of the pancreas. GLP-1 and GIP/GLP-1 medications like Mounjaro may trigger it in susceptible individuals, though the exact mechanism is not fully understood. It's rare — less than 0.5% in clinical trials — but requires immediate medical attention if suspected.
How does pancreatitis risk compare between Mounjaro and Wegovy?
Both medications show comparable, low pancreatitis rates in clinical trials. Mounjaro's dual GIP+GLP-1 mechanism versus Wegovy's GLP-1-only approach does not result in meaningfully different pancreatitis risk. Individual factors matter more than the medication type.
What should I tell my prescriber before starting Mounjaro to reduce pancreatitis risk?
Disclose any history of pancreatitis, gallstones, gallbladder disease, or high triglycerides. Also mention any family history of medullary thyroid cancer or multiple endocrine neoplasia type 2. Your prescriber uses this to assess whether either medication is suitable for you.
Can I use the GLP-1 weight loss calculator if I'm concerned about pancreatitis risk?
Yes — use our free GLP-1 weight loss calculator to explore potential weight loss outcomes, but always discuss pancreatitis risk with your prescriber during your clinical assessment. The calculator helps you understand the medication context, not medical suitability.
If I'm taking Mounjaro and develop stomach pain, what should I do?
If you experience severe, persistent stomach pain spreading to your back, stop taking Mounjaro immediately and seek emergency medical care. Do not wait — pancreatitis is a medical emergency. Call 999 or go to A&E.
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