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 in the UK and NHS — What You Need to Know
Wegovy (semaglutide) is a prescription-only weight loss injection available in the UK through both NHS specialist services and private online prescribing. If you're considering Wegovy as part of a weight management plan, it's important to understand how NHS access works, eligibility criteria, and how it compares to alternative medications like Mounjaro. This guide covers everything UK adults need to know about accessing Wegovy through the NHS or privately, including how it works and what to expect.
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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.
How Wegovy Works and How It Compares to Mounjaro
Wegovy (semaglutide) is a GLP-1 receptor agonist — it activates a single hormone pathway to help regulate appetite and reduce food cravings. Mounjaro (tirzepatide) works differently: it's a dual GIP and GLP-1 agonist, activating two hormone pathways simultaneously.
- Mechanism: Wegovy uses one pathway; Mounjaro uses two, which may explain differences in clinical trial results
- Clinical trial data (STEP-1): Wegovy showed average weight loss of approximately 14.9% body weight over 68 weeks at the maximum 2.4 mg dose
- Clinical trial data (SURMOUNT-1): Mounjaro showed average weight loss of approximately 20.9% body weight over 72 weeks at the maximum 15 mg dose
- Individual variation: Both medications produce different results in different people — trial averages do not predict individual outcomes
Both are once-weekly injections, both require a prescription, and both must be used alongside reduced-calorie diet and increased physical activity for best results.
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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 and Eligibility for Wegovy in the UK
In the UK, Wegovy has been approved by NICE (National Institute for Health and Care Excellence) for use within NHS specialist weight management services. However, NHS access is not straightforward: you must be referred to a tier 3 or tier 4 specialist weight management service by your GP, and availability varies significantly by region.
You may be eligible for NHS prescription 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. South Asian, Chinese, Black African, and Black Caribbean adults may have access at lower BMI thresholds.
Waiting lists for NHS specialist services can be very long — often months to years depending on your area. Private prescribing offers faster access: you can obtain a prescription through a UK-licensed online prescriber following a clinical assessment, dispensed by a GPhC-registered pharmacy. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses.
- 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.
Can I get Wegovy on the NHS in the UK?
Wegovy is NICE-approved for NHS use, but access is through specialist tier 3/4 weight management services via GP referral. Availability and waiting times vary significantly by region. Many areas have substantial waiting lists. Private prescribing offers faster access following an online clinical assessment.
What's the difference between Wegovy and Mounjaro?
Wegovy (semaglutide) is a GLP-1 agonist activating one hormone pathway. Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist activating two pathways. Clinical trials showed different average weight loss results, but individual outcomes vary significantly. Both require prescription and clinical assessment.
How much weight can I expect to lose with Wegovy?
Clinical trial data (STEP-1) showed average weight loss of approximately 14.9% body weight over 68 weeks at 2.4 mg. However, individual results vary considerably. Weight loss depends on dose, adherence, diet, physical activity, and personal metabolism. Use our GLP-1 calculator for estimated projections based on your circumstances.
What are the main side effects of Wegovy in the UK?
Very common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain — usually mild and temporary during dose escalation. Common side effects include indigestion, headache, fatigue, and injection site reactions. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and allergic reactions. Always report persistent symptoms to your GP.
Is Wegovy better than Mounjaro for weight loss?
Clinical trials showed higher average weight loss with Mounjaro, but "better" depends on individual suitability, tolerability, and health circumstances. A prescriber will assess whether Wegovy or Mounjaro is more appropriate for you based on your BMI, health conditions, medications, and personal factors. Both require clinical assessment before prescription.
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.