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 You Need to Know
Pancreatitis is a serious but rare side effect associated with Mounjaro (tirzepatide) and other GLP-1 medications. Although uncommon, it requires immediate medical attention if symptoms develop. This guide explains what pancreatitis is, warning signs to watch for, and what to do if you suspect this complication whilst taking Mounjaro. Always consult your GP or healthcare professional if you have concerns about your individual risk or experience any severe symptoms.
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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: The Facts
Pancreatitis is inflammation of the pancreas, a gland that produces digestive enzymes and hormones. Mounjaro may increase the risk of acute pancreatitis, though this remains rare in clinical practice. The exact mechanism is not fully understood, but GLP-1 and tirzepatide activation may affect pancreatic function or gallstone formation, which can trigger inflammation.
Key facts:
- Pancreatitis was reported in clinical trials but occurred in a small percentage of participants
- Risk may be higher in people with a personal or family history of pancreatitis
- People with severe gallbladder disease have increased risk
- Symptoms typically appear within weeks of starting Mounjaro or increasing the dose
- Stopping Mounjaro and seeking urgent medical care significantly improves outcomes
Unlike common side effects such as nausea or constipation, pancreatitis is a medical emergency and requires immediate hospital 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 Help
Seek urgent medical attention (call 111 or go to A&E) immediately if you experience:
- Sudden severe pain in the upper abdomen spreading to the back
- Persistent vomiting or inability to keep food or fluids down
- Abdominal tenderness or swelling
- Fever above 38°C
- Rapid heartbeat or difficulty breathing
These symptoms require emergency assessment to rule out pancreatitis or other serious conditions. Even if you are uncertain, it is better to seek medical evaluation than to wait. Your GP or the NHS 111 service can advise whether A&E assessment is needed. Do not continue taking Mounjaro if you suspect pancreatitis — inform medical staff immediately that you are taking this medication.
- 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 common with Mounjaro?
No. Pancreatitis is a rare side effect reported in clinical trials at a low frequency. Most people taking Mounjaro experience common side effects like nausea, constipation, or diarrhoea instead. However, because pancreatitis is serious, any suspected symptoms warrant immediate medical evaluation, even though the risk remains small.
Who is at higher risk of pancreatitis with Mounjaro?
People with a personal or family history of pancreatitis, those with gallstones or severe gallbladder disease, and those with certain triglyceride disorders may have elevated risk. Your GP or prescriber can assess your individual risk before starting Mounjaro and may recommend alternative treatments if risk is high.
How does Mounjaro compare to Wegovy regarding pancreatitis risk?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are GLP-1 medications with rare pancreatitis risk reported in clinical trials. Mounjaro uses a dual GIP and GLP-1 mechanism whilst Wegovy uses GLP-1 alone, but pancreatitis risk is similar. Individual risk depends more on personal health factors than the specific medication.
What should I do if I experience severe abdominal pain whilst taking Mounjaro?
Do not wait or assume it is a common side effect. Contact NHS 111 immediately or attend A&E. Inform medical staff that you are taking Mounjaro (tirzepatide). Severe upper abdominal pain spreading to the back is a red flag symptom requiring urgent hospital assessment to confirm or exclude pancreatitis.
Can I restart Mounjaro after pancreatitis?
No. If you develop pancreatitis whilst taking Mounjaro, the medication should be stopped permanently. Restarting carries a high risk of recurrence. Your GP or prescriber will discuss alternative weight management strategies or medications if appropriate for your individual situation.
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