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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What Is The Risk Of Pancreatitis With Mounjaro?
Pancreatitis is a serious inflammation of the pancreas that requires urgent medical attention. Whilst pancreatitis is not listed as a common side effect of Mounjaro (tirzepatide), it is an important safety consideration that you should understand before starting this prescription-only injection. This guide explains what pancreatitis is, the warning signs to watch for, and when to contact your GP or seek emergency care if you suspect a problem.
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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.
Understanding Pancreatitis Risk With Mounjaro
Pancreatitis occurs when the pancreas becomes inflamed, usually triggered by gallstones or high triglycerides (blood fats). Whilst clinical trial data for tirzepatide does not show pancreatitis as a frequent side effect, healthcare professionals remain alert to this risk because GLP-1 receptor agonists can theoretically affect pancreatic function.
The risk is very small but real. Key warning signs of acute pancreatitis include:
- Severe, persistent upper abdominal pain (often spreading to the back)
- Severe abdominal tenderness
- Nausea and vomiting that won't stop
- Rapid pulse or sweating
- Fever
If you experience these symptoms whilst taking Mounjaro, contact your GP immediately or attend an A&E department. Do not wait for your next scheduled dose. Your prescriber needs to know about any severe abdominal pain so they can assess whether this is pancreatitis or another condition requiring urgent evaluation.
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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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Accessing Mounjaro Safely In The UK
Before starting Mounjaro, your prescriber will review your full medical history to assess your individual risk factors. This includes checking whether you have a personal or family history of pancreatitis, gallbladder problems, or high triglycerides—all factors that increase pancreatitis risk.
Mounjaro is available through NHS specialist weight management services (tier 3) or via private prescription following an online clinical assessment with a UK-licensed prescriber. Whichever route you choose, the assessment process ensures your suitability. Your GP can also refer you to NHS services if you meet eligibility criteria. Throughout treatment, regular monitoring helps catch any complications early, and you should always report severe abdominal symptoms to your healthcare provider immediately.
- 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 are the early signs of pancreatitis I should watch for with Mounjaro?
Early warning signs include severe, persistent upper abdominal pain (especially pain spreading to your back), severe tenderness in the stomach area, nausea and vomiting, rapid heartbeat, and fever. If you experience these symptoms, contact your GP immediately or attend A&E. Do not wait—pancreatitis is a medical emergency.
Is pancreatitis a common side effect of Mounjaro?
Pancreatitis is not listed as a common side effect in clinical trials of tirzepatide. However, it is a recognised risk with GLP-1 receptor agonist medications. The absolute risk is very small, but it's important to know the warning signs and seek urgent help if severe abdominal pain develops.
How can my prescriber assess my pancreatitis risk before I start Mounjaro?
Your prescriber will ask about your medical history, including any previous pancreatitis, gallstones, very high triglycerides, or family history of pancreatic disease. They may order blood tests to check your triglyceride levels. This assessment helps determine whether Mounjaro is safe for you personally.
Can I use the MyWeightCheck BMI calculator to check if I'm eligible for Mounjaro?
Our free BMI calculator helps you understand your current BMI and whether you fall into weight ranges where prescription treatment might be considered. However, eligibility for Mounjaro also depends on weight-related health conditions and medical history—always discuss your suitability with your GP or a licensed prescriber.
What's the difference between Mounjaro and Wegovy in terms of pancreatitis risk?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are GLP-1 receptor agonists with similar pancreatitis risk profiles, though Mounjaro is a dual GIP and GLP-1 agonist. Clinical trials show the risk is very low for both. Your prescriber will assess which is more suitable based on your individual health circumstances and medical history.
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