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 and Mounjaro — What UK Patients Should Know
Pancreatitis is a rare but serious side effect that can occur with Mounjaro (tirzepatide), the prescription-only weight management injection licensed in the UK. While uncommon, it's important to recognise the warning signs and know when to seek urgent medical attention. This guide explains what pancreatitis is, how it relates to tirzepatide use, and what to do if you experience concerning symptoms. If you're considering Mounjaro or already taking it, understanding this risk is part of making an informed decision alongside your prescriber.
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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 with Mounjaro — What the Evidence Shows
Pancreatitis — inflammation of the pancreas — is listed as a rare side effect of Mounjaro in the UK Product Information. In clinical trials and real-world use, the incidence is uncommon, but healthcare professionals monitor for it carefully because it can be serious if not a UK pharmacy promptly.
What happens: The pancreas becomes inflamed, disrupting its ability to produce digestive enzymes and insulin. This can cause acute (sudden) pancreatitis or, rarely, chronic pancreatitis with repeated episodes.
Why it might occur: The exact mechanism is not fully understood, but GIP and GLP-1 receptor agonists like tirzepatide may affect pancreatic function directly or indirectly through changes in how the stomach empties. gradual weight management itself can also trigger gallstone formation, which is a known trigger for pancreatitis.
Risk factors that may increase likelihood: History of pancreatitis, gallstones or gallbladder disease, high triglycerides, and certain medications. Your prescriber will assess these during your clinical assessment.
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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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Symptoms of Pancreatitis — When to Seek Emergency Care
Seek immediate emergency medical attention if you experience:
- Severe, persistent upper abdominal pain that spreads to your back
- Pain that worsens when you eat or move
- Nausea or vomiting
- Fever
- Yellowing of the skin or eyes (jaundice)
- Rapid heartbeat
These symptoms require assessment at A&E (Accident & Emergency). Do not wait — acute pancreatitis can be life-threatening if left untreated. If you develop these symptoms while taking Mounjaro, contact emergency services or attend A&E immediately and inform them you are taking tirzepatide.
- 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 in the UK?
Pancreatitis is rare with tirzepatide. Clinical trials and post-market surveillance data show very low incidence rates. However, because it is serious, healthcare professionals monitor for it and patients should know the warning signs. Your GP or prescriber can discuss your individual risk based on your medical history.
Can I prevent pancreatitis while taking Mounjaro?
There is no assured prevention, but you can reduce risk by: attending all follow-up appointments, informing your prescriber of any history of pancreatitis or gallstones, maintaining adequate hydration, eating balanced meals to support pancreatic health, and reporting any concerning symptoms immediately. Use our free BMI calculator and progress tracker to monitor your weight loss journey safely alongside medical supervision.
If I've had pancreatitis before, can I take Mounjaro?
A history of pancreatitis may be a contraindication or require careful assessment by your prescriber. This must be discussed during your clinical assessment before Mounjaro is prescribed. Your prescriber will weigh the benefits and risks specific to your situation. Do not start Mounjaro without declaring your full medical history.
What's the difference between Mounjaro and Wegovy regarding pancreatitis risk?
Both tirzepatide (Mounjaro) and semaglutide (Wegovy) are GLP-1-based medications with pancreatitis listed as a rare side effect. Mounjaro is a dual GIP/GLP-1 agonist, while Wegovy is a GLP-1 agonist only. Individual risk may vary, but both carry similar warnings. Your prescriber will help choose the appropriate option based on your medical profile.
Should I stop Mounjaro if I'm worried about pancreatitis?
Do not stop Mounjaro suddenly without speaking to your prescriber — abrupt discontinuation can affect your health. If you have concerns about pancreatitis risk, contact your GP or the healthcare provider who prescribed it to discuss your worries and review whether the medication remains appropriate for you. They can also explain your individual risk level based on your health profile.
Ready to take control of your weight loss journey?
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