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 Surgery in the UK — What You Need to Know
Weight loss surgery in the UK is available through both the NHS and private healthcare, but eligibility depends on your BMI, health conditions, and other factors. Surgery is typically considered the last resort after other weight management approaches have been tried. This guide explains NHS access, typical costs, BMI requirements, and what the assessment process involves. Use our free BMI calculator above to check where you stand — it will help you understand your eligibility for different treatment options.
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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.
Understanding Weight Loss Surgery and BMI Requirements
Weight loss surgery (bariatric surgery) is offered through NHS specialist tier 4 weight management services and privately. NHS eligibility generally requires a BMI of 40 or above, or BMI of 35–39.9 with significant weight-related health conditions like type 2 diabetes or sleep apnoea. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, NHS guidelines recommend lower thresholds — typically BMI 35 or above.
Types of bariatric surgery available in the UK include gastric bypass, gastric sleeve, gastric band, and duodenal switch. Each procedure works differently to reduce food intake or calorie absorption.
Private weight loss surgery may accept lower BMI thresholds and typically has shorter waiting times (weeks rather than months or years), but costs range from £7,000 to £15,000+ depending on the procedure and provider.
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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.
Next Steps: From Assessment to Weight Loss Support
If you're considering weight loss surgery, the NHS pathway starts with your GP. Ask for a referral to your local tier 3 or tier 4 specialist weight management service, though waiting lists vary significantly by region — some are 12+ months. Before surgery, you'll need a full health assessment, psychological evaluation, and confirmation that you've tried other weight management approaches.
Non-surgical alternatives like prescription GLP-1 weight loss injections (Mounjaro or Wegovy) are now available through NHS specialist services and privately, and may be worth exploring first. Our GLP-1 weight loss calculator can help you project potential outcomes. Whatever route you choose, sustainable weight loss is most successful alongside lifestyle changes — diet, physical activity, and behaviour support are essential.
- 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.
What BMI do you need for weight loss surgery on the NHS?
NHS eligibility is typically BMI 40 or above, or BMI 35–39.9 with weight-related health conditions. For South Asian, Chinese, Black African, or Black Caribbean adults, lower thresholds may apply (BMI 35+). Your GP can discuss eligibility and refer you to a specialist service.
How much does weight loss surgery cost privately in the UK?
Private weight loss surgery typically costs £7,000 to £15,000+, depending on the procedure type and clinic. Gastric bypass is often more expensive than gastric sleeve. Some private insurers cover bariatric surgery, so check your policy. Always get a detailed quote before proceeding.
How long is the NHS waiting list for weight loss surgery?
NHS waiting times for bariatric surgery vary by region and local commissioning. Many areas have waits of 12 months or longer. Private surgery can often be arranged within weeks. Ask your specialist service for a realistic timeframe for your region.
Is weight loss surgery the only option if I'm overweight or obese?
No. Surgery is typically tier 4 (last resort). NHS recommends trying tier 1–3 interventions first: lifestyle changes, weight management programmes, GP support, and — if eligible — prescription weight loss medication like Mounjaro or Wegovy. Your GP can discuss all options with you.
What's the difference between NHS and private weight loss surgery?
NHS is free but has long waiting lists and stricter eligibility criteria. Private is faster (weeks) and more flexible on BMI thresholds, but costs £7,000–£15,000+. Both use the same surgical techniques. Private may offer more choice of surgeon and hospital. Neither is "better" — it depends on your timeline and budget.
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.