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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Semaglutide GLP-1: NHS Weight Management in the UK
Semaglutide is a GLP-1 receptor agonist — a prescription-only weight management injection licensed in the UK under the brand name Wegovy. This guide explains how semaglutide works, UK NHS eligibility criteria, clinical trial results from the STEP studies, and the two main routes to access this medication: through NHS specialist weight management services or privately. Understanding your options helps you make an informed decision with your GP.
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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.
NHS Eligibility and Tier 3 Weight Management Services
The NHS has approved semaglutide (Wegovy) for weight management through specialist tier 3 services. You may be eligible if you have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 with a weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease.
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply — eligibility may begin at BMI 27.5 or above due to higher health risks at lower weights. To access NHS semaglutide treatment, you'll need a GP referral to your local tier 3 weight management service. These services provide comprehensive assessment, prescription, monitoring, and ongoing support alongside dietary and lifestyle advice. Use our free BMI calculator above to check if you may fall within eligible ranges, and discuss your options with your GP to understand local availability in your area.
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.
STEP Trial Evidence and NHS vs Private Routes
The STEP-1 clinical trial showed that semaglutide helped participants lose an average of approximately 14.9% of body weight over 68 weeks when combined with a reduced-calorie diet and increased physical activity. Individual results vary significantly. In the UK, you can access semaglutide through two main routes: NHS specialist services (following GP referral, often with waiting lists) or private prescribing (through online clinical assessments with UK-licensed prescribers). Both require clinical assessment to confirm suitability. Private access typically offers faster access but involves out-of-pocket costs. Try our GLP-1 weight loss calculator to estimate potential outcomes at different dose levels, and discuss which route suits your circumstances with your healthcare provider.
- 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.
How does semaglutide work as a GLP-1 receptor agonist?
Semaglutide mimics the natural GLP-1 hormone produced in your gut after eating. It signals fullness to your brain, helps you feel satisfied after smaller meals, slows how quickly food leaves your stomach, and regulates blood sugar. This dual effect on appetite and satiety supports sustainable weight management.
What is the difference between Wegovy and Ozempic semaglutide?
Both contain semaglutide but are different medications. Ozempic (up to 2 mg) is licensed for type 2 diabetes management. Wegovy (up to 2.4 mg) is the licensed weight management version. Using Ozempic for weight loss is off-label. In the UK, Wegovy is the approved semaglutide option for weight management.
How long are NHS waiting lists for semaglutide weight management?
Waiting times vary significantly by region and local tier 3 service capacity. Some areas have waiting lists of several months or longer. Contact your local weight management service through your GP referral to understand current waiting times in your area.
Can I get semaglutide prescribed privately while on an NHS waiting list?
Yes. You can pursue private prescribing while waiting for NHS assessment. However, inform both your GP and private prescriber that you're registered with NHS services to ensure coordinated care and avoid duplicate monitoring.
What happens after I reach my target weight on semaglutide?
Your prescriber will discuss ongoing management — this may involve continuing at a maintenance dose, gradually stepping down, or stopping treatment. Weight regain is common if treatment stops without lifestyle changes. Discuss long-term strategy with your GP or prescriber.
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.