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 Operations in the UK
A weight loss operation refers to several types of surgical and non-surgical interventions designed to support weight management. In the UK, options range from bariatric surgery on the NHS to prescription weight management injections available privately. Understanding what's available, how each works, and whether you might be eligible is essential before deciding on any weight management approach. Your GP can help assess which option is right for your individual health needs.
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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.
Types of Weight Loss Operations Available
Bariatric surgery is the main surgical weight loss operation in the UK. The NHS funds several types for adults with severe obesity (typically BMI 40 or above, or BMI 35 with weight-related health conditions). Common surgical options include:
- Gastric bypass: Reduces stomach size and alters how food is digested. Average weight loss: 60–70% of excess weight.
- Gastric band: A belt tightens around the stomach to limit food intake. Average weight loss: 40–50% of excess weight.
- Sleeve gastrectomy: Removes part of the stomach, reducing capacity. Average weight loss: 50–60% of excess weight.
- Duodenal switch: Combines stomach reduction with intestinal bypass. Average weight loss: 70–80% of excess weight.
Non-surgical alternatives have become increasingly available for weight management UK. Prescription weight loss medications like GLP-1 injections offer a less invasive route and are now accessible through NHS weight management services and private prescription routes for eligible adults.
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 Access to Weight Loss Operations
Access to bariatric surgery through the NHS is a tier 4 intervention on the NHS weight loss pathway. You'll typically need to be referred by your GP after completing tier 1–3 interventions (self-help, behaviour change programmes, and specialist weight management services). Assessment involves checks for physical fitness for surgery, psychological readiness, and confirmation that you'll commit to post-operative lifestyle changes. Waiting times vary significantly by region. Newer prescription weight management injections offer faster access as prescription weight loss UK alternatives — available through private online prescribing without NHS waiting lists. Use our free GLP-1 weight loss calculator to explore non-surgical options and their potential impact on your weight.
- 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's the difference between bariatric surgery and weight loss injections?
Bariatric surgery is invasive, with permanent stomach changes and significant weight loss but surgical risks. Weight loss injections like Mounjaro and Wegovy are non-surgical, reversible, and administered at home, though results vary individually. Both require commitment to lifestyle changes.
How much weight can you lose with a weight loss operation?
Surgical outcomes depend on the procedure type. Gastric bypass averages 60–70% excess weight loss; sleeve gastrectomy 50–60%; duodenal switch 70–80%. GLP-1 injections average 15–21% total body weight loss in clinical trials, though individual results vary significantly.
Can you get bariatric surgery on the NHS?
Yes, the NHS funds bariatric surgery for adults with severe obesity (BMI 40+, or BMI 35+ with comorbidities). You'll need referral through your GP to a tier 4 specialist service and assessment. Waiting times vary by region; some areas have significant delays.
What happens after weight loss surgery?
Post-surgery requires lifelong dietary changes, regular monitoring, and often vitamin supplementation. You'll need follow-up appointments with your surgical team. Most people can return to normal activities within 6–8 weeks, though full recovery takes longer.
Are weight loss injections an alternative to surgery?
Yes. GLP-1 medications like Wegovy offer a non-surgical alternative for eligible adults (BMI 30+, or 27+ with weight-related health conditions). They're prescription-only and work alongside diet and exercise. Unlike surgery, they're reversible but require ongoing prescription. Check your BMI using our free BMI calculator to explore options.
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.