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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Gallbladder Pain on Mounjaro — What You Need to Know
Gallbladder pain is a potential side effect of weight loss injections like Mounjaro (tirzepatide) and Wegovy (semaglutide). Both are GLP-1 receptor agonist medications — Mounjaro also acts as a dual GIP receptor agonist — licensed for weight management in the UK. If you experience sharp pain in the upper right side of your stomach, back pain between the shoulder blades, or nausea after taking either medication, it's important to contact your GP immediately. This guide compares how these medications affect gallbladder health and what you should know before starting treatment.
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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 and Wegovy Differ in Gallbladder Risk
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) can cause gallbladder problems because they slow gastric emptying — how quickly food leaves the stomach. This mechanism may increase bile stasis (bile pooling in the gallbladder), potentially increasing gallstone formation risk. Clinical trial data from SURMOUNT (Mounjaro) and STEP (Wegovy) trials both reported gallbladder-related adverse events, though the exact incidence varies:
- Mounjaro: Gallbladder problems reported in clinical trials; requires monitoring during dose titration from 2.5 mg to 15 mg across weeks 1–20+
- Wegovy: Gallbladder events documented in STEP trials; dose escalation occurs more gradually from 0.25 mg to 2.4 mg over 17+ weeks
Neither medication is absolutely contraindicated in people with gallbladder disease, but both require prescriber assessment. Use our GLP-1 weight loss calculator to understand dose progression and discuss gallbladder risk factors with your GP before starting either medication.
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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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When to Seek Medical Help and Prescriber Guidance
Seek urgent medical attention if you experience severe upper abdominal pain radiating to your back, persistent nausea, vomiting, or jaundice (yellowing of skin or eyes) — these may indicate acute cholecystitis or pancreatitis. Tell your prescriber if you have a history of gallstones, previous gallbladder surgery, or biliary colic before starting Mounjaro or Wegovy. Your UK prescriber — whether through NHS specialist tier 3 services or private online assessment — must evaluate your individual gallbladder risk. If you're concerned about gallbladder health, ask for baseline ultrasound imaging before starting treatment. Both medications require ongoing monitoring, and either can be discontinued if gallbladder complications arise.
- 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 I take Mounjaro if I've had gallstones in the past?
Possibly, but requires prescriber assessment. Previous gallstones increase your risk of recurrence on GLP-1 medications. Inform your GP or prescriber of your full medical history. They may recommend imaging before starting and closer monitoring during dose titration. Do not start treatment without clinical evaluation of your gallbladder risk.
Is Wegovy safer than Mounjaro for gallbladder problems?
Both carry similar gallbladder risk because both slow gastric emptying. Wegovy's slower dose escalation (0.25 mg to 2.4 mg) might theoretically reduce risk compared to Mounjaro's faster titration, but clinical trial data do not show one is significantly safer than the other. Individual risk depends on your personal factors, not the medication alone.
What are the early signs of gallbladder problems on these injections?
Early warning signs include right upper abdominal pain, pain between shoulder blades, nausea after eating fatty foods, and discomfort lasting 30 minutes to several hours. These don't always mean gallstones — they could be general GI side effects — but warrant GP contact. Severe or persistent pain requires urgent assessment.
Can I use the BMI calculator to check if I'm eligible if I have gallbladder issues?
Our free BMI calculator shows whether your BMI falls in the NHS weight management range (30+, or 27+ with health conditions), but BMI alone doesn't determine suitability if you have gallbladder concerns. Always discuss your full medical history, including any gallbladder disease, with your GP or prescriber before treatment.
How is gallbladder risk monitored once I start Mounjaro or Wegovy?
Your prescriber should ask about abdominal symptoms at follow-up appointments during dose titration. If symptoms develop, they may pause escalation, switch medication, or refer you for ultrasound imaging. Report any new abdominal pain immediately — do not wait for your next scheduled appointment.
Ready to take control of your weight loss journey?
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