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 You Need to Know
Pancreatitis is a serious side effect associated with Mounjaro (tirzepatide) and other GLP-1 weight loss medications. Although it is rare, it is important to recognise the warning signs and know when to seek emergency medical care. This guide explains what pancreatitis is, how it relates to Mounjaro, the symptoms to watch for, and what to do if you experience severe abdominal pain. Always consult your GP or prescriber if you have concerns about this risk.
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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 is inflammation of the pancreas, a gland that produces digestive enzymes and hormones that regulate blood sugar. It is a medical emergency and requires urgent hospital assessment.
In clinical trials and post-market surveillance of Mounjaro (tirzepatide), pancreatitis has been reported but remains rare. The exact mechanism is not fully understood, though GLP-1 and GIP receptor agonists may affect pancreatic function. Some pancreatitis cases have been associated with gradual weight management, very low calorie intake, or gallstones — all factors that can occur during weight loss treatment.
- Acute pancreatitis develops suddenly and requires immediate hospital care
- Chronic pancreatitis develops over time with repeated inflammation
- Your prescriber should assess your risk factors before starting Mounjaro, including any history of pancreatic disease or gallstones
The UK's MHRA (Medicines and Healthcare products Regulatory Agency) monitors all reports of pancreatitis linked to weight loss medications and includes this risk in the official product information.
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If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
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Symptoms of Pancreatitis — When to Seek Emergency Care
Seek emergency medical attention (call 999 or go to A&E) if you experience severe abdominal pain, especially pain in the upper abdomen that spreads to the back, particularly if combined with vomiting, nausea, or fever. These are classic signs of acute pancreatitis.
Other warning symptoms include rapid heartbeat, yellowing of the skin or eyes (jaundice), persistent indigestion, or swelling of the abdomen. Do not wait for these symptoms to resolve — pancreatitis requires immediate hospital assessment and blood tests to confirm diagnosis.
If you have any history of pancreatic problems, gallstones, or high triglycerides, inform your GP or prescriber before starting Mounjaro. They can help you weigh the benefits and risks and monitor you more closely. Always report any new or unusual abdominal symptoms to your prescriber promptly.
- 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 is the actual risk of pancreatitis with Mounjaro in the UK?
Pancreatitis is rare with Mounjaro. Clinical trials and post-market data show it is an uncommon side effect. However, because it is serious, it is listed as a potential risk in the official information. Your prescriber will assess your individual risk factors — such as history of gallstones, high triglycerides, or previous pancreatic disease — before prescribing. Not everyone on Mounjaro will experience pancreatitis, but you should know the warning signs.
Can I continue Mounjaro if I have a history of gallstones?
This depends on your individual risk assessment. Gallstones and gradual weight management can increase pancreatitis risk. Your GP or specialist prescriber must know about any gallstone history before you start Mounjaro. They may recommend additional monitoring, may suggest an alternative weight loss approach, or may decide Mounjaro is still appropriate for you. Never start Mounjaro without disclosing your full medical history.
Is pancreatitis more likely with Mounjaro than with Wegovy?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) carry a rare pancreatitis risk because both are GLP-1 receptor agonists. Mounjaro is a dual GIP and GLP-1 agonist, which may carry a theoretically different risk profile, but clinical data do not show a significant difference in pancreatitis rates between the two. Your prescriber will help you understand the relative risks.
What happens if I develop pancreatitis while on Mounjaro?
Pancreatitis is a UK pharmacy in hospital. If you suspect pancreatitis, call 999 or go to A&E immediately. Hospital staff will perform blood tests (including amylase and lipase levels) and imaging to confirm diagnosis. Treatment may include IV fluids, pain management, and dietary support. Most cases resolve with treatment, though recovery depends on severity. Once you have had pancreatitis, Mounjaro will usually need to be stopped permanently.
How can I reduce my risk of pancreatitis while on Mounjaro?
Follow your prescriber's dose titration schedule — do not skip doses or increase faster than recommended. Maintain a balanced, nutritious diet rather than very low calorie intake. Stay well hydrated. If you have risk factors like gallstones or high triglycerides, attend all monitoring appointments and blood tests. Report any abdominal pain, nausea, or unusual symptoms immediately. Use our free BMI calculator and GLP-1 weight loss calculator to track your progress safely and discuss results with your prescriber.
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