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 Effective Is Wegovy For Weight Loss in the UK?
Wegovy (semaglutide) is a prescription-only weekly weight loss injection that has shown meaningful effectiveness in clinical trials, with average weight loss of around 15% of body weight in UK patients. However, individual results vary significantly, and Wegovy works best alongside dietary changes and physical activity. Access through the NHS is available in some areas via tier 3 specialist weight management services, though private prescribing is also an option for eligible adults. Use our free GLP-1 weight loss calculator above to explore potential outcomes at different doses.
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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.
Wegovy Effectiveness: STEP Trial Data and NHS Context
Clinical trial results: The STEP-1 trial, which underpins Wegovy's UK approval, showed participants lost an average of approximately 15% of body weight over 68 weeks at the maximum dose of 2.4 mg once weekly. This translates to roughly 10–15 kg for many adults, though outcomes vary considerably based on starting weight, adherence, and lifestyle factors.
NHS eligibility for Wegovy: You may be eligible through the NHS if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. For people of South Asian, Chinese, Black African, or Caribbean heritage, lower BMI thresholds apply. Access is through tier 3 specialist weight management services following GP referral — availability varies significantly by region and ICB.
- Results are achieved with a reduced-calorie diet and increased physical activity
- The medication is typically continued long-term; weight often returns when treatment stops
- Compared to semaglutide for diabetes (Ozempic), Wegovy uses a higher approved dose (2.4 mg vs 2 mg maximum)
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 vs Private Access: How to Get Wegovy in the UK
NHS route: Request a referral from your GP to a tier 3 weight management service. Waiting lists can be lengthy (months to years in some areas), and not all regions fund Wegovy. Once prescribed, you receive it through NHS dispensing at no cost.
Private route: Consult with a UK-registered prescriber through a GPhC-regulated online pharmacy. Clinical assessment is required; if suitable, a prescription is issued and dispensed privately. Costs range from approximately £129–£320 per month depending on dose. This route avoids NHS waiting lists but requires personal payment.
- Both routes require a clinical assessment confirming eligibility
- Prescription is essential — Wegovy cannot be purchased without one
- Check your BMI using our free BMI calculator above to understand your starting point
- 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 much weight do most people lose on Wegovy?
In the STEP-1 clinical trial, participants lost an average of approximately 15% of their body weight over 68 weeks. For a 100kg adult, this would be around 15kg. However, individual results vary — some lose more, some less — depending on starting weight, adherence to dietary changes, physical activity, and individual metabolism. Results are not assured.
Is Wegovy more effective than Mounjaro for weight loss?
Clinical data suggests Mounjaro (a dual GIP and GLP-1 agonist) may produce slightly higher average weight loss (15–21%) than Wegovy (around 15%), but direct head-to-head trials are limited. Both are effective weekly weight loss injections. The best choice depends on individual health factors, assessed during a clinical consultation. Your prescriber can advise which is more suitable for you.
How long does Wegovy take to work?
Weight loss typically becomes noticeable within 4–8 weeks, as doses are gradually increased. Maximum effectiveness is usually reached around 16 weeks (once you reach the 2.4 mg maintenance dose). However, appetite suppression and reduced food cravings may be felt within days of the first injection in some individuals.
What happens to weight loss when you stop Wegovy?
Weight loss is not permanent if Wegovy is stopped. Clinical data shows weight gradually returns over time once treatment ends. This is why Wegovy is designed as a long-term treatment. Combining it with sustainable lifestyle changes (diet and exercise) gives the best chance of maintaining progress if you eventually discontinue the medication.
Can I access Wegovy through the NHS in my area?
This depends on your local NHS Integrated Care Board (ICB). Some regions fund Wegovy through tier 3 weight management services; others have limited availability or longer waiting lists. Your GP can advise on local access. Private prescribing through a GPhC-registered online pharmacy is an alternative if NHS access is unavailable or you prefer to avoid waiting lists.
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.