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
Free tracker included with every download this week
Gallstones And Weight Loss: UK Medication Options
Gallstones can develop or worsen during gradual weight management, which is an important health consideration for anyone planning to lose weight. If you have a history of gallstones, prescription weight management medication may still be suitable for you — but requires careful medical assessment. In the UK, several prescription-only medicines are available to support weight loss when combined with lifestyle changes. This guide explains your options, NHS eligibility, and how to discuss gallstone risk with your GP.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
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.
UK-Licensed Prescription Weight Management Options
Three prescription-only medicines are currently licensed in the UK for weight management in eligible adults: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). All are GLP-1 receptor agonist medications (Mounjaro is a dual GIP/GLP-1 agonist) that help regulate appetite and support feeling fuller after smaller meals.
In clinical trials, these medications helped participants lose an average of 15–21% of body weight alongside reduced-calorie diets and increased physical activity — though individual results vary significantly. Eligibility for prescription weight loss medication in the UK requires a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. South Asian, Chinese, Black African, or Black Caribbean adults may have access at lower BMI thresholds due to higher health risks at these weights.
Importantly, if you have a history of gallstones, your prescriber must assess this during your clinical evaluation. Some individuals with gallstone history can safely use these medications, whilst others may not be suitable — this is determined on a case-by-case basis.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
NHS And Private Access In The UK
NHS access: Prescription weight loss medication is available through NHS specialist weight management services (tier 3), typically following referral from your GP. However, availability varies significantly by region, and waiting lists can be long in many areas. During your NHS assessment, your medical history — including any gallstone complications — will be reviewed.
Private access: Weight management medications are also available through GPhC-registered online pharmacies following an online clinical assessment. A UK-licensed prescriber will review your health history, including gallstone risk factors, before issuing a prescription. Private treatment costs typically range from £129–£320 per month depending on dose and provider.
Whether accessing through NHS or private routes, always inform your prescriber about any gallstone history or digestive concerns. Your GP can advise on which pathway is most appropriate for your individual circumstances.
- 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 use Mounjaro or Wegovy if I have a history of gallstones?
This depends on your individual medical history and the severity of your gallstone condition. Some people with resolved gallstone issues can safely use GLP-1 medications, whilst active gallbladder disease or recent complications may contraindicate them. Your prescriber must assess this during clinical evaluation — always disclose your full gallstone history. Your GP can advise before referral.
Why do gallstones develop during weight loss?
gradual weight management can increase gallstone formation because the liver secretes more cholesterol into bile during fat mobilisation, and reduced food intake decreases gallbladder contractions. Slower, gradual weight loss — approximately 0.5–1 kg per week — reduces this risk compared to very rapid loss. This is one reason medical support is important.
Will my GP refer me for prescription weight loss medication if I have gallstones?
Your GP will consider your full medical picture, including gallstone history. They may refer you to a specialist weight management service where healthcare professionals can assess whether GLP-1 medication is safe for you. Some people with gallstone history are suitable candidates; others may not be. Assessment is individual.
What is the safest rate of weight loss if I have gallstone risk?
The NHS recommends losing no more than 0.5–1 kg per week for sustainable, safer weight loss. This slower rate reduces gallstone formation risk compared to rapid loss. Using our free progress tracker can help you monitor steady weight loss and stay within this safe range.
Should I discuss gallstone risk with my prescriber before starting weight loss medication?
Absolutely. Always inform your prescriber — whether NHS or private — about any history of gallstones, gallbladder surgery, or digestive complications. This is essential information for clinical assessment. Your prescriber will use this to determine safety and suitability for prescription weight loss treatment. Don't omit medical history details.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.