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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Mounjaro and Pancreatitis — What UK Adults Need to Know
Pancreatitis is a serious but rare side effect of Mounjaro (tirzepatide) that requires immediate medical attention. This guide explains what pancreatitis is, the warning signs to watch for, UK prescribing context, and when to contact your GP or emergency services. Understanding this risk helps you use Mounjaro safely alongside a reduced-calorie diet and increased physical activity.
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Calculate Your BMI Instantly
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.
Understanding Pancreatitis and Mounjaro Risk
Pancreatitis is inflammation of the pancreas, a gland that produces digestive enzymes and hormones. GLP-1 and GIP/GLP-1 agonists like Mounjaro can, in rare cases, trigger pancreatitis. This risk is documented in clinical trials and UK prescribing information.
Key facts about Mounjaro-related pancreatitis:
- Very rare — affects a small percentage of users
- More common in people with a history of gallbladder or pancreatic disease
- Can occur at any dose during dose titration or maintenance
- Usually develops within the first weeks of starting or increasing dose
- Requires immediate medical evaluation if suspected
If you have a personal or family history of pancreatitis or gallbladder disease, inform your prescriber before starting Mounjaro. Your GP or the prescriber conducting your clinical assessment will evaluate your individual risk.
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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.
Warning Signs and When to Seek Emergency Care
Seek immediate emergency care (call 999 or attend A&E) if you experience:
- Severe stomach pain in the upper abdomen spreading to the back
- Nausea and vomiting alongside severe abdominal pain
- Pain that worsens when lying flat or eating fatty foods
- Rapid or painful heartbeat with abdominal pain
- Yellowing of skin or eyes (possible jaundice)
Do not wait for a GP appointment if you have severe abdominal pain — go to A&E immediately. Contact your GP as soon as possible if you develop mild stomach pain, indigestion, or nausea that concerns you, as early evaluation is important. Your NHS team or prescriber needs to know about any gastrointestinal symptoms.
- 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 common is pancreatitis with Mounjaro?
Pancreatitis is very rare with Mounjaro. Clinical trial data shows it occurs in a small percentage of users. Risk is higher if you have a personal or family history of pancreatic or gallbladder disease. Your prescriber will assess your individual risk during clinical assessment before prescribing.
What does pancreatitis pain feel like?
Pancreatitis typically causes severe, sudden pain in the upper abdomen that spreads to the back. Pain often worsens when lying flat or eating, and may be accompanied by nausea, vomiting, or fever. Seek emergency care immediately if you experience these symptoms.
Can I continue Mounjaro if I have mild stomach pain?
Contact your GP or prescriber about any stomach pain. Mild indigestion is common with Mounjaro, but severe pain requires urgent evaluation. Your prescriber may pause your dose or investigate further. Never ignore severe abdominal pain — go to A&E immediately.
What should I tell my GP before starting Mounjaro?
Inform your GP or prescriber if you have a history of pancreatitis, gallbladder disease, gallstones, or thyroid cancer. Also mention any family history of these conditions. This helps your prescriber assess whether Mounjaro is safe for you and monitor you appropriately during treatment.
Is pancreatitis risk higher at certain Mounjaro doses?
Pancreatitis risk is not significantly higher at maximum doses, but can occur during any stage of dose titration or maintenance. Your prescriber will monitor you throughout treatment. Report any new symptoms immediately rather than waiting to reach your target dose.
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.