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
How to Prevent Gallstones During Weight Loss
gradual weight management can increase your risk of developing gallstones, a condition where hard deposits form in the gallbladder. This is particularly important if you're using prescription weight loss medication like Wegovy or pursuing aggressive weight management in the UK. The good news is that several evidence-based strategies can significantly reduce this risk whilst still achieving your weight loss goals safely and sustainably.
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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.
Why Gallstones Form During Weight Loss
When you lose weight quickly, your body breaks down stored fat for energy. This process releases cholesterol into the bile, increasing the concentration of cholesterol gallstones. The NHS warns that gradual weight management—typically more than 1.5 kg per week—significantly raises gallstone risk. This is especially relevant if you're using GLP-1 weight loss medication like Wegovy (semaglutide), which can lead to faster weight loss than diet alone. Clinical trials show that participants using Wegovy experience average weight loss of approximately 15% of body weight, which may accelerate gallstone formation if weight loss progresses too quickly.
- Cholesterol concentration in bile increases during gradual weight management
- Risk is highest in the first 2–8 weeks of gradual weight management
- Women, those over 40, and people with a higher starting BMI face increased risk
- Pre-existing gallbladder problems increase vulnerability
Understanding these mechanisms helps you plan safer weight management strategies. Use our free BMI calculator to determine your current BMI and assess your baseline health risk before starting any weight loss programme.
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.
Safe Strategies to Reduce Gallstone Risk
Gradual weight loss is key: The NHS recommends losing 0.5–1 kg per week for sustainable, safer results. If using prescription weight loss injections, your prescriber will manage your dose escalation to balance rapid results with safety. Include adequate dietary fat—at least 20–30% of daily calories—as this helps trigger gallbladder contractions and prevent bile stasis. Stay well hydrated by drinking 6–8 glasses of water daily, which supports healthy bile flow and digestion. Maintain regular physical activity, even modest movement like daily walking, as exercise reduces gallstone risk independent of weight loss. If your NHS weight management team or private prescriber recommends a very low-calorie diet (under 800 kcal daily), request close monitoring and consider temporary ursodeoxycholic acid (a gallstone prevention medication) if clinically indicated.
- 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 Wegovy or other GLP-1 injections cause gallstones?
GLP-1 medications like Wegovy don't directly cause gallstones, but the gradual weight management they enable can increase risk. Slowed gastric emptying may also temporarily reduce gallbladder contractions. Your prescriber will monitor you and can discuss preventive strategies if needed.
What's the safest rate of weight loss to avoid gallstones?
The NHS recommends losing 0.5–1 kg per week as the safe range that minimises gallstone risk whilst still achieving meaningful results. Faster loss carries higher risk and may cause muscle loss alongside fat loss.
Should I eat fat if I'm trying to lose weight and prevent gallstones?
Yes—paradoxically, adequate dietary fat (around 20–30% of calories) stimulates gallbladder contractions and helps prevent bile stasis. Extremely low-fat diets actually increase gallstone risk, so avoid them without medical guidance.
What symptoms suggest gallstones are developing?
Sudden pain in the upper right abdomen, under the right shoulder blade, or right shoulder can indicate gallstones. Nausea, vomiting, or pain after fatty meals are also warning signs. Seek urgent medical advice if you experience these symptoms.
Does using our weight loss calculator help prevent gallstone risk?
Yes—our GLP-1 weight loss calculator shows realistic projections based on gradual dose escalation, helping you understand expected weight loss rates and plan safer weight management aligned with NHS recommendations.
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.