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
Free tracker included with every download this week
What Is Wegovy?
Wegovy is a prescription-only weight management injection containing semaglutide, licensed in the UK for adults with obesity or overweight with health conditions. It works by activating GLP-1 receptors in the brain to help reduce appetite and support feeling fuller after smaller meals. Unlike Ozempic (which is approved for type 2 diabetes only), Wegovy is specifically licensed for weight management. Clinical trials showed participants lost an average of around 15% of their body weight, though individual results vary significantly. It's used alongside dietary changes and increased physical activity, not as a standalone treatment.
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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 What to Expect
Semaglutide is a GLP-1 receptor agonist — it mimics and amplifies the action of a natural gut hormone called glucagon-like peptide-1 (GLP-1). This hormone signals to your brain that you're satisfied, reducing appetite and cravings. Wegovy slows how quickly food leaves your stomach, helping you feel fuller for longer after meals.
Wegovy is given as a once-weekly injection using a pre-filled pen. Treatment starts at a low dose (0.25 mg) and gradually increases over weeks — each dose is held for at least 4 weeks before escalating. The maximum dose is 2.4 mg once weekly. Weight loss typically becomes noticeable after 4–8 weeks, with most significant loss occurring over 12–20 weeks. Results depend on individual factors including genetics, diet adherence, and physical activity levels.
- Prescription-only medicine — requires clinical assessment
- Once-weekly injection — self-administered at home
- Gradual dose escalation — typically over 16–20 weeks to reach 2.4 mg
- Works best with reduced-calorie diet and exercise
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.
Wegovy Eligibility and Getting It in the UK
You may be eligible for Wegovy if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Use our free BMI calculator to check your BMI instantly. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recognises lower BMI thresholds due to higher health risks at the same weight.
Wegovy is available through NHS specialist weight management services (tier 3) or private online prescribing following a clinical assessment. Access via the NHS requires a GP referral and varies significantly by region — waiting lists can be lengthy. Private prescribing offers faster access without an NHS referral. A licensed prescriber will assess your health history, current medications, and suitability before issuing a prescription. Track your progress with our free progress tracker once treatment begins.
- 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 the same as Ozempic?
No. Both contain semaglutide, but Ozempic is licensed for type 2 diabetes management (up to 2 mg dose) and is not approved for weight loss in the UK. Wegovy is specifically approved for weight management at a higher dose (up to 2.4 mg). Using Ozempic for weight loss would be off-label prescribing.
How much weight will I lose on Wegovy?
Clinical trials (STEP-1) showed an average weight loss of around 14.9% of body weight over 68 weeks at the maximum 2.4 mg dose. Individual results vary significantly based on genetics, diet, exercise, and adherence. Some people lose more, others less — a prescriber can discuss realistic expectations for you personally.
What are the main side effects of Wegovy?
Very common side effects include nausea, diarrhoea, vomiting, and constipation — typically mild and reducing over time as your body adjusts. Common side effects include indigestion, headache, fatigue, and injection site reactions. Serious side effects are rare but can include severe stomach pain (possible pancreatitis) — seek immediate medical attention if this occurs.
How does Wegovy compare to Mounjaro?
Wegovy (semaglutide, GLP-1 agonist) and Mounjaro (tirzepatide, dual GIP+GLP-1 agonist) are both once-weekly injections for weight management. Clinical trials suggest similar average weight loss (~15%), but Mounjaro may be slightly more effective. Both require prescription and clinical assessment. Our GLP-1 weight loss calculator can help you explore potential outcomes with either medication.
Do I need to stay on Wegovy indefinitely?
Wegovy is typically used long-term, as weight often returns when treatment stops. Your prescriber will discuss treatment duration based on your response and health goals. Some people use it for extended periods; others may pause or stop if weight loss goals are reached and maintained through diet and exercise alone. Regular monitoring with your prescriber is essential.
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.