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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Pancreatitis on Mounjaro vs Wegovy — What UK Adults Need to Know
Pancreatitis is a serious but rare side effect that can occur with weight loss injections. Both Mounjaro (tirzepatide) and Wegovy (semaglutide) carry a small risk of acute pancreatitis, and this risk is monitored carefully in clinical trials and real-world use. Understanding how these medications compare in terms of pancreatitis risk, warning signs, and safety monitoring is important if you're considering prescription weight loss treatment in the UK. This guide explains what the evidence shows and when to seek immediate medical help.
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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.
Pancreatitis Risk: Clinical Trial Data and Safety Profiles
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that underwent rigorous safety testing in the SURMOUNT clinical trials before UK approval. Acute pancreatitis was reported in fewer than 1% of participants across SURMOUNT studies. Wegovy (semaglutide) is a GLP-1-only receptor agonist tested in the STEP trials, where pancreatitis also occurred in less than 1% of participants. Both medications carry a black triangle (▼) monitoring status with the MHRA, meaning ongoing pharmacovigilance is required. The actual risk of pancreatitis in real-world use remains very low, but because pancreatitis is serious, any severe stomach pain must be reported to your GP immediately. Your prescriber will assess individual risk factors—such as a personal or family history of pancreatitis, gallstones, or high triglycerides—before initiating either Mounjaro UK prescription or Wegovy treatment.
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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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When to Seek Medical Help and Individual Suitability Assessment
Warning signs of pancreatitis include sudden severe pain in the upper abdomen that spreads to your back, often accompanied by nausea or vomiting. Contact your GP or go to A&E immediately if you experience these symptoms. Your prescriber will discuss your personal risk factors during your clinical assessment before starting either medication. Use our free GLP-1 weight loss calculator to understand how these medications work and what to expect, and our BMI calculator to establish your baseline health status. Neither Mounjaro nor Wegovy is suitable for people with a history of severe pancreatitis or medullary thyroid cancer. The choice between them depends on your individual health profile, dose titration response, and prescriber recommendation—both require ongoing monitoring by a healthcare professional.
- 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.
Is pancreatitis more likely on Mounjaro than Wegovy?
Clinical trial data shows pancreatitis risk is similarly very low for both medications (less than 1%). The dual mechanism of Mounjaro (GIP plus GLP-1) differs from Wegovy's single GLP-1 mechanism, but pancreatitis risk appears comparable. Individual risk depends on personal factors like gallstone history or triglyceride levels, not the medication type.
What are the early warning signs of pancreatitis?
Seek immediate medical attention if you develop sudden severe upper abdominal pain spreading to your back, persistent nausea or vomiting, or tenderness in the upper abdomen. These symptoms warrant a same-day GP visit or A&E attendance. Do not wait—pancreatitis is a medical emergency.
Can I take Mounjaro if I have a family history of pancreatitis?
A family history of pancreatitis does not automatically exclude you from GLP-1 or tirzepatide treatment, but your GP or prescriber must assess your individual risk. They may recommend additional monitoring or suggest Wegovy as an alternative if they believe your personal risk profile is lower with a GLP-1-only medication.
Does dose titration affect pancreatitis risk on Mounjaro?
Mounjaro dose titration is gradual by design—starting at 2.5 mg and increasing every 4 weeks—to allow your body to adjust and minimise side effects. The escalation process itself does not increase pancreatitis risk; it's a safety measure. Pancreatitis risk remains consistent across dose levels.
What happens if I develop pancreatitis while on a weight loss injection?
Stop the medication immediately and seek emergency medical care. Your GP will confirm diagnosis via blood tests (amylase and lipase levels). If pancreatitis is confirmed, you cannot resume that medication. Your prescriber will discuss alternative weight management approaches tailored to your health status.
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