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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Is Wegovy Safe? NHS UK Guide to Semaglutide
Wegovy (semaglutide) is a prescription-only GLP-1 receptor agonist licensed for weight management in UK adults. If you're wondering whether Wegovy is safe, the evidence suggests it is, when prescribed by a qualified healthcare professional following a proper clinical assessment. The UK medicines regulator (MHRA) has approved Wegovy, and the National Institute for Health and Care Excellence (NICE) has reviewed it positively for use within NHS specialist weight management services. However, like all medications, Wegovy does carry side effects and isn't suitable for everyone. Understanding how Wegovy works, who can safely take it, and what to expect is essential before starting treatment. Use our free GLP-1 weight loss calculator above to explore potential outcomes with semaglutide, and read on for comprehensive NHS and UK-specific safety information.
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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 Safety in the UK: NHS and NICE Context
Wegovy has been approved by the MHRA and recommended by NICE for use in UK specialist weight management services, which means it has undergone rigorous safety and efficacy assessment. The STEP clinical trials demonstrated that semaglutide is effective for weight loss, with participants losing an average of approximately 14.9% of their body weight over 68 weeks — though individual results vary significantly.
Wegovy is safe for most adults meeting NHS eligibility criteria: those with a BMI of 30 or above, or 27 to 29.9 with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or obstructive sleep apnoea. However, Wegovy is not suitable for anyone under 18, pregnant, breastfeeding, or with a history of certain thyroid conditions.
The most common side effects are gastrointestinal — nausea, diarrhoea, vomiting, and constipation. These typically decrease over time as your body adjusts to each dose. Serious side effects are rare but can include pancreatitis (severe stomach pain), gallbladder problems, or allergic reactions. Your prescriber will assess whether Wegovy is appropriate for your individual health profile.
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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 vs Private Routes for Wegovy in the UK
NHS access: Wegovy is available through NHS tier 3 specialist weight management services, typically after referral from your GP. However, NHS availability varies significantly by region, and waiting lists can be lengthy — in some areas, waiting times exceed 12 months. Your GP will assess whether you meet local NHS eligibility criteria.
Private access: Wegovy is also available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. This route offers faster access without NHS referral, though you'll pay privately (typically £150–£280 monthly depending on dose). Both routes require a prescription — Wegovy cannot be legally purchased without one in the UK. Compare your options with your GP or use our BMI calculator to confirm your eligibility status.
- 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.
Is Wegovy approved by the UK health authorities?
Yes. Wegovy (semaglutide) is licensed by the MHRA and has been positively reviewed by NICE for use in UK specialist weight management services. It has undergone rigorous safety and efficacy assessment, and clinical trial data supports its use for weight management in eligible adults.
What are the main safety concerns with Wegovy?
The most common side effects are mild gastrointestinal symptoms — nausea, diarrhoea, constipation, and vomiting — which often improve as your body adjusts. Rare serious risks include pancreatitis, gallbladder problems, and changes in thyroid function. Your prescriber will assess your suitability before prescribing.
Who should not take Wegovy?
Wegovy is not suitable for anyone under 18, pregnant or breastfeeding, with a personal or family history of thyroid cancer, or with medullary thyroid carcinoma. It's also not recommended for those with severe gastroparesis. Your GP or prescriber will check these contraindications during assessment.
Can I get Wegovy through the NHS in the UK?
Yes, but access varies by region. Wegovy is available through NHS tier 3 specialist weight management services, typically via GP referral. However, waiting times can be several months to over a year depending on your area. Private access is available through online prescribing services with faster availability.
How does Wegovy compare to Mounjaro for safety in the UK?
Both are licensed and considered safe when prescribed appropriately. Wegovy (semaglutide) is a GLP-1 receptor agonist, while Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist. Mounjaro may produce slightly greater average weight loss, but both carry similar gastrointestinal side effects. Your prescriber will advise which is more suitable for you.
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.