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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Weight Loss Medication After Gallstones Removal
After gallstone removal, many people struggle with weight management due to changes in how the body processes fat and food. In the UK, several prescription weight management options are available for eligible adults, including GLP-1 medications that may help support sustainable weight loss alongside lifestyle changes. This guide explains which medications are licensed in the UK, how to find out if you're eligible, and how to discuss options with your GP. Use our free BMI calculator to understand your current weight status and track progress with our free progress tracker as you work toward your goals.
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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.
UK-Licensed Prescription Weight Loss Options
Three main prescription medications are licensed in the UK for weight management and may be suitable following gallstone removal:
- Mounjaro (tirzepatide) — a once-weekly injection that activates two hormone pathways (GIP and GLP-1). Clinical trials showed participants lost an average of 15–21% of body weight over 72 weeks alongside a reduced-calorie diet and increased physical activity. Starting dose is 2.5 mg, escalating to a maximum of 15 mg per week.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. Clinical trials demonstrated average weight loss of around 15% of body weight. Doses range from 0.25 mg to 2.4 mg weekly.
- Saxenda (liraglutide) — a daily GLP-1 injection for weight management, doses 0.6 mg to 3 mg per day.
All three are prescription-only and require a clinical assessment. Your prescriber will assess whether medication is suitable based on your individual health history and current BMI. Try our free GLP-1 weight loss calculator to explore potential outcomes at different doses.
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
NHS vs Private Access and How to Find Out If You're Eligible
In the UK, you can access prescription weight loss medication through two routes:
- NHS: Referral to a specialist tier 3 or tier 4 weight management service through your GP. Eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, cardiovascular disease). NHS availability varies significantly by region and waiting lists can be lengthy.
- Private: Online consultation with a UK-licensed prescriber followed by prescription from a registered pharmacy. No NHS referral required. Costs range from approximately £129–£320 monthly depending on dose.
Start by speaking with your GP about your weight management goals post-surgery. They can assess your BMI, discuss your medical history, and advise on the best route for you. Use our free BMI calculator to check your current status before your appointment.
- 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 weight loss injections after having my gallbladder removed?
Possibly, but you must discuss this with your GP or prescriber first. After gallstone removal, your body processes dietary fat differently, which can affect how medications are absorbed. Your prescriber will assess your individual situation, recovery status, and whether prescription weight loss medication is appropriate for you at this time.
What's the difference between Mounjaro and Wegovy for weight management?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials showed Mounjaro participants lost slightly more weight on average (15–21% vs 15%), but both are effective. Both are once-weekly injections. Your prescriber will recommend the most suitable option based on your health profile.
How long does it take to see weight loss results with GLP-1 medication?
Most people begin to notice weight changes within 4–8 weeks of starting treatment, though individual responses vary. Medications are titrated (dose gradually increased) over 16–20 weeks to reach a maintenance dose. Sustainable weight loss continues over months of treatment. Results are most effective when combined with a reduced-calorie diet and increased physical activity.
What happens to my weight if I stop taking the medication?
Weight loss may plateau or reverse if you stop taking GLP-1 medication without maintaining the lifestyle changes (diet and exercise) that supported it. Many people continue treatment long-term to maintain results. Discuss duration and stopping plans with your prescriber — they can advise on what's best for your situation.
How do I know if I'm eligible for NHS weight loss medication?
Generally, you're eligible if you have a BMI of 30 or above, or 27–29.9 with at least one weight-related health condition (type 2 diabetes, high blood pressure, sleep apnoea, cardiovascular disease). Your GP can assess your eligibility and refer you to a specialist weight management service. Use our BMI calculator to check your current BMI before speaking with your GP.
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.