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 Risk: Mounjaro and Wegovy Compared
Pancreatitis is a rare but serious side effect associated with GLP-1 receptor agonist medications, including Mounjaro (tirzepatide) and Wegovy (semaglutide). Both medications carry a warning about potential pancreatitis risk, though cases are uncommon in clinical trials. Understanding the symptoms, risk factors, and how these dual and single-mechanism injections compare is essential for anyone considering GLP-1 weight loss treatment in the UK. Your prescriber will assess your individual risk during clinical assessment before prescribing.
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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: Clinical Trial Data and Mechanism Differences
Pancreatitis is inflammation of the pancreas, a serious condition requiring immediate medical attention. In clinical trials, pancreatitis was a rare adverse event in both groups.
Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist — is approved for UK weight management via a KwikPen device. In the SURMOUNT-1 trial, pancreatitis was reported in a small percentage of participants, with no clear dose-dependent relationship.
Wegovy (semaglutide) — a GLP-1-only agonist — is also approved for UK weight loss. The STEP trials similarly reported rare cases of pancreatitis across all doses.
- Both medications are GLP-1 pathway activators, which theoretically could affect pancreatic function
- Mounjaro's dual GIP + GLP-1 mechanism differs from Wegovy's single GLP-1 pathway, but pancreatitis risk remains low in both
- Clinical trial incidence suggests pancreatitis is uncommon with either medication when used as prescribed
- Neither drug is recommended for those with a personal or family history of pancreatitis or pancreatic disease
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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.
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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Individual Risk Assessment and Prescriber Guidance
Your prescriber will assess your pancreatitis risk during clinical assessment before prescribing Mounjaro or Wegovy. You should inform your prescriber of any personal or family history of pancreatitis, gallbladder disease, or pancreatic conditions.
Seek urgent medical attention if you develop:
- Severe, persistent abdominal pain that radiates to the back
- Nausea or vomiting lasting several hours
- High fever (38°C or above)
- Rapid or irregular heartbeat
- Yellowing of skin or eyes (jaundice)
These symptoms may indicate pancreatitis or other serious pancreatic complications. Do not delay — call 999 or attend A&E immediately. Both Mounjaro and Wegovy require prescription and ongoing clinical monitoring.
- 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 more common with Mounjaro or Wegovy?
Clinical trials show pancreatitis is rare with both medications. Mounjaro uses a dual GIP + GLP-1 mechanism while Wegovy uses GLP-1 only, but reported pancreatitis rates are similarly low in both SURMOUNT and STEP trials. Individual risk varies based on personal health history, assessed by your prescriber during clinical assessment.
What are the early warning signs of pancreatitis?
Early signs include severe abdominal pain (especially upper abdomen radiating to the back), persistent nausea or vomiting, fever, and loss of appetite. These symptoms warrant urgent medical attention. Do not wait — contact NHS 111 or attend A&E immediately if you suspect pancreatitis.
Can I use Mounjaro or Wegovy if I have a family history of pancreatic disease?
Inform your prescriber of any personal or family history of pancreatitis, cystic fibrosis, or gallbladder disease. Your prescriber may advise against these medications or recommend additional monitoring. Clinical assessment is essential — never start GLP-1 medication without full disclosure of your medical history.
Is pancreatitis a reason to stop Mounjaro or Wegovy?
If you develop symptoms of pancreatitis, stop the medication immediately and seek emergency medical care. Pancreatitis is a medical emergency. After recovery, your prescriber will reassess whether continuing GLP-1 treatment is safe. Do not restart without explicit medical guidance.
How do GLP-1 injections affect pancreatic function?
GLP-1 receptor agonists stimulate insulin release and regulate blood sugar — normally beneficial pancreatic functions. However, rare cases of pancreatitis have been reported. The mechanism is not fully understood. This is why clinical assessment and informed consent are crucial before starting Mounjaro or Wegovy in the UK.
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