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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Wegovy for Weight Loss in the UK
Wegovy (semaglutide) is a prescription-only weekly weight loss injection that has been approved in the UK for adults with obesity or overweight with related health conditions. In clinical trials, this semaglutide weekly weight loss injection helped participants lose an average of around 15% of their body weight over 68 weeks, though individual results vary significantly. Access in the UK is available through both NHS specialist weight management services and private prescription routes. It works as a GLP-1 receptor agonist, meaning it helps reduce appetite and supports feeling fuller after smaller meals. Eligibility depends on your BMI and health circumstances, which your GP or a licensed prescriber can assess.
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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 Prescribing Routes for Wegovy
Wegovy eligibility in the UK follows NICE guidance and applies to adults with a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower BMI thresholds due to higher health risks at these weights.
NHS access is through specialist tier 3 or tier 4 weight management services — not standard GP prescription. You typically require a referral from your GP, though waiting lists for NHS services vary significantly by region and ICB (Integrated Care Board). Some areas have waiting times of several months or longer.
- NICE has approved semaglutide for use in specialist NHS weight management services
- Wegovy is prescribed at doses from 0.25 mg up to 2.4 mg once weekly
- Clinical trial data (STEP-1) showed average weight loss of approximately 14.9% body weight at the maximum dose
- Treatment is used alongside a reduced-calorie diet and increased physical activity — not as a standalone intervention
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 Routes for Getting Wegovy in the UK
The NHS specialist route offers prescriptions through dedicated weight management services, but availability is limited and waiting lists can be substantial. Private prescription routes are available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber — this can be faster but requires payment (typically £129–£320+ per month depending on dose).
Regardless of route, a prescriber will assess whether Wegovy is clinically appropriate for you based on your individual health, BMI, any weight-related conditions, and medications you take. Use our free GLP-1 weight loss calculator to estimate potential weight loss projections at different doses, and our BMI calculator to check whether your current weight falls within NHS eligibility ranges. Combination therapy — Wegovy plus lifestyle change — produces the best results.
- 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.
Am I eligible for Wegovy on the NHS?
NHS eligibility requires a BMI of 30 or above, or 27–29.9 with a weight-related health condition like diabetes or hypertension. You must be referred to a specialist tier 3 weight management service by your GP. Ethnicity can affect thresholds — discuss with your GP whether you qualify.
How long does Wegovy take to work?
Weight loss typically becomes noticeable within 4–8 weeks, with progressive results over 12–16 weeks. The STEP-1 trial showed average weight loss of around 15% over 68 weeks at the maximum 2.4 mg dose, but individual results vary based on diet, activity, and personal factors.
What's the difference between Wegovy and Mounjaro?
Wegovy (semaglutide) is a single GLP-1 receptor agonist, while Mounjaro (tirzepatide) activates both GIP and GLP-1 pathways. Clinical trial data suggests Mounjaro may produce slightly higher average weight loss, but both are effective. Your prescriber will advise which is more suitable for you.
What are the main side effects of Wegovy?
Most common side effects are nausea, diarrhoea, vomiting, and constipation — typically mild and temporary during dose increases. Serious side effects are rare but can include severe stomach pain (possible pancreatitis) or gallbladder issues. Always report persistent or severe symptoms to your prescriber.
Can I get Wegovy faster through private prescription?
Yes, private routes can be faster — typically days to weeks rather than months. Private prescriptions cost £129–£320+ monthly depending on dose and provider. Both routes require a clinical assessment confirming suitability and eligibility for the medication.
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.