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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Weight Loss Injections: Wegovy in the UK
Wegovy (semaglutide) is a once-weekly weight loss injection licensed in the UK for adults with obesity or overweight with health conditions. It works by activating the GLP-1 hormone pathway to help reduce appetite and support feeling fuller after meals. Available through both NHS specialist services and private prescribing, Wegovy is part of a growing range of prescription weight management options. This guide covers NHS eligibility, how to access Wegovy, and what to expect. Check your BMI using our free BMI calculator to see if you may be eligible.
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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.
NHS Eligibility and Access for Wegovy
Wegovy eligibility in the UK follows NHS guidelines: adults with a BMI of 30 kg/m² or above, or BMI of 27–29.9 kg/m² with at least one weight-related health condition (type 2 diabetes, prediabetes, high blood pressure, abnormal blood fats, or cardiovascular disease). For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply.
Access via the NHS is through tier 3 specialist weight management services, typically initiated by GP referral. NICE has approved semaglutide (the active ingredient in Wegovy) for use within NHS specialist weight management services, though availability varies significantly by region and waiting lists can be lengthy. Clinical trials (STEP-1 study) showed that Wegovy helped participants lose an average of 14.9% of body weight over 68 weeks when combined with lifestyle changes.
- Tier 3 services provide multidisciplinary support alongside medication
- Requires clinical assessment and ongoing monitoring
- Cost to NHS varies by region
- Waiting times can exceed 12 months in some areas
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.
Private vs NHS Access: Which Route for Wegovy?
NHS route: Free at point of use if prescribed through tier 3 services, but requires GP referral, specialist assessment, and often involves significant waiting times. You gain support from a multidisciplinary team (dietician, nurse, psychologist).
Private route: Available through GPhC-registered online prescribing services following a clinical assessment. This offers faster access (typically within days) without NHS waiting lists, though costs range from approximately £129–£280 per month depending on dose. Private prescribers assess your suitability and issue a prescription dispensed by regulated pharmacies. Many people choose private access when NHS waiting times are long or their local tier 3 service has limited availability. Use our free weight loss calculator to estimate potential outcomes and help inform discussions with a prescriber.
- 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 Wegovy and how does it work for weight loss?
Wegovy (semaglutide) is a once-weekly injectable GLP-1 receptor agonist that mimics a natural hormone (GLP-1) produced in the gut. It signals to your brain that you're full, helps reduce food cravings, and slows how quickly food leaves your stomach. Clinical trials showed participants lost an average of 14.9% of body weight over 68 weeks alongside lifestyle changes.
Am I eligible for Wegovy through the NHS in the UK?
You may be eligible if you have a BMI of 30 kg/m² or above, or BMI of 27–29.9 kg/m² with a weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease. People of South Asian, Chinese, Black African, or Black Caribbean heritage may have lower BMI eligibility thresholds. Ask your GP about referral to a tier 3 specialist weight management service.
How long does it take to access Wegovy through the NHS?
Waiting times vary significantly by region. Many areas have waiting lists of 6–18 months or longer for tier 3 services. Private access is typically faster (days to weeks) but involves a cost. Contact your local integrated care board (ICB) for information about waiting times in your area.
What is the difference between Wegovy and Mounjaro?
Wegovy (semaglutide) is a single GLP-1 receptor agonist, while Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist. Clinical trials showed Wegovy resulted in average weight loss of 14.9%, and Mounjaro achieved 15–clinically studied weight loss. Individual results vary considerably. Both are prescription-only and require clinical assessment.
What are the common side effects of Wegovy?
Very common side effects include nausea, diarrhoea, vomiting, and constipation, typically mild and improving over time. Common effects include indigestion, headache, fatigue, and injection site reactions. Serious side effects are rare but can include severe stomach pain (possible pancreatitis) or gallbladder problems. Always discuss side effects with your prescriber or GP.
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.