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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How to Get a Wegovy Prescription in the UK
Wegovy (semaglutide) is a prescription-only weight management injection available in the UK through both NHS specialist services and private prescribing. Understanding how to access Wegovy, what the eligibility criteria are, and how it compares to Mounjaro can help you make an informed decision about prescription weight loss treatment. This guide covers everything you need to know about Wegovy prescriptions in the UK, including how it works, what to expect, and the differences between the main GLP-1 and dual-action weight loss injections available today.
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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.
Wegovy vs Mounjaro: Key Differences and Trial Data
Wegovy and Mounjaro are the two most commonly prescribed weight loss injections in the UK, but they work differently. Wegovy is a GLP-1 receptor agonist — it activates a single hormone pathway to reduce appetite and support feeling fuller. Mounjaro is a dual GIP and GLP-1 receptor agonist — it activates two hormone pathways, which may explain why some clinical trials show slightly higher average weight loss.
Clinical trial results: In the STEP-1 trial, Wegovy (semaglutide 2.4 mg) helped participants lose an average of approximately 15% of their body weight over 68 weeks. In the SURMOUNT-1 trial, Mounjaro (tirzepatide 15 mg) helped participants lose an average of approximately 21% of body weight over 72 weeks. However, individual results vary considerably, and both medications work best alongside a reduced-calorie diet and increased physical activity. Your prescriber will assess which option suits your individual health needs, medical history, and previous weight loss attempts.
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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
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UK Eligibility and How to Access Wegovy on Prescription
To get a Wegovy prescription in the UK, you must meet NHS eligibility criteria: a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related health condition (such as type 2 diabetes, high blood pressure, or cardiovascular disease). For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply due to higher health risks at lower weights.
Access routes: NHS referral goes through your GP to a tier 3 specialist weight management service — waiting times vary significantly by region. Private access is available through a UK-licensed prescriber via online consultation; if clinically appropriate, a prescription is issued and dispensed by a GPhC-registered pharmacy. Use our free GLP-1 weight loss calculator to explore projected weight loss at different doses, and 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.
What is the difference between Wegovy and Ozempic?
Both contain semaglutide but are licensed differently. Ozempic is approved for type 2 diabetes (doses up to 2 mg) and is not licensed for weight loss in the UK. Wegovy is the licensed weight management version (doses up to 2.4 mg). Using Ozempic for weight loss would be off-label. Always use the medication prescribed by your healthcare provider.
How long does it take to see weight loss results with Wegovy?
Weight loss typically begins within the first few weeks, but the most significant results occur over 12–16 weeks as your dose increases. Clinical trials showed weight loss over 68 weeks. Results vary individually, and Wegovy works best alongside dietary changes and physical activity. Consistency matters more than speed.
Can I get Wegovy on the NHS in the UK?
Yes, Wegovy is available through NHS tier 3 specialist weight management services if you meet eligibility criteria. Referral is through your GP, but availability and waiting times vary significantly by region (ICB). Some areas have substantial waiting lists. Private prescribing offers faster access if you meet clinical criteria.
What are the main side effects of Wegovy?
Common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain — especially when starting or increasing doses. Most side effects reduce over time as your body adjusts. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and allergic reactions. Always report new or worsening symptoms to your prescriber.
Is Wegovy better than Mounjaro for weight loss?
Clinical trials show Mounjaro may deliver slightly higher average weight loss (21% vs 15%), but individual results vary significantly. Suitability depends on your personal health history, previous medications, and what a prescriber assesses as clinically appropriate for you. Neither is universally "better" — the right choice is individual.
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.