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 Your Pancreas — What You Need to Know
Mounjaro (tirzepatide) is a prescription-only weight management injection that works by activating hormone pathways in your body. Many people wonder about pancreas safety when considering any new medication. Understanding how Mounjaro affects pancreatic function is important for informed decision-making. This guide explains the relationship between tirzepatide and pancreas health, based on clinical evidence and UK medical guidance. If you're considering Mounjaro or already taking it, your GP can provide personalised advice about your individual health status.
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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.
How Mounjaro Works and Pancreatic Function
Mounjaro is a dual GIP and GLP-1 receptor agonist — it activates two natural hormone pathways in your body. These pathways help regulate blood sugar, appetite, and how your body uses food. The pancreas produces insulin and other hormones; Mounjaro doesn't directly replace or damage pancreatic tissue. Instead, it enhances your body's natural signalling, which may actually support better blood sugar control.
In clinical trials like SURMOUNT-1, Mounjaro was generally well tolerated. The pancreas itself remains structurally intact during treatment. However, very rarely, any GLP-1 or GIP medication can trigger acute pancreatitis — inflammation of the pancreas. This is a serious but uncommon side effect requiring immediate medical attention. Signs include severe stomach pain spreading to your back, nausea, and vomiting. If you experience these symptoms whilst taking Mounjaro, contact your GP or call 111 immediately.
People with a history of pancreatitis or pancreatic cancer should discuss this carefully with their prescriber before starting Mounjaro, as the medication may not be suitable.
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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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Pancreatic Safety and Mounjaro Monitoring
Mounjaro is prescription-only and requires clinical assessment before dispensing. A healthcare professional will review your full medical history, including any pancreatic conditions, before determining if the medication is safe for you. This assessment is crucial — it means you won't be prescribed Mounjaro if there are contraindications related to your pancreas or digestive system.
During treatment, you should report any unusual stomach pain, persistent nausea, or changes in digestion to your GP promptly. Pancreatitis risk is rare but serious. The benefit of weight management with Mounjaro, alongside lifestyle changes and our GLP-1 weight loss calculator to track progress, must be weighed against individual risk factors. Your prescriber will monitor you and can adjust or stop treatment if needed. Always take Mounjaro exactly as prescribed and attend follow-up appointments.
- 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.
Can Mounjaro damage your pancreas?
Mounjaro doesn't structurally damage the pancreas. It works by enhancing natural hormone signalling. However, very rarely, it may trigger pancreatitis (pancreas inflammation). This is uncommon and usually develops early in treatment. Seek immediate care if you experience severe abdominal pain spreading to your back.
Is Mounjaro safe if I have a history of pancreatitis?
If you have had pancreatitis before, you must inform your prescriber. Mounjaro may not be suitable, or your doctor may recommend careful monitoring. Never start Mounjaro without discussing previous pancreatic issues with a healthcare professional.
What are the signs of pancreatitis whilst taking Mounjaro?
Warning signs include severe, sudden stomach pain (often in the upper abdomen spreading to the back), persistent nausea, vomiting, and fever. These symptoms require urgent medical attention. Contact your GP, call 111, or go to A&E. Do not wait or assume it will pass.
How does Mounjaro compare to Wegovy regarding pancreas safety?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are GLP-1-related medications with similar rare pancreatitis risk profiles. Mounjaro is a dual GIP/GLP-1 agonist whilst Wegovy is GLP-1 only, but both require the same clinical assessment and monitoring for pancreatic safety.
Do I need pancreas tests before starting Mounjaro?
Your prescriber will ask about your medical history, including pancreatic health. Routine blood tests may be performed. These pre-treatment checks help identify if Mounjaro is safe for you. Your GP will decide which tests, if any, are necessary based on your individual situation.
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