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
Semaglutide Wegovy — What You Need to Know
Semaglutide is the active ingredient in Wegovy, a prescription-only weight management injection licensed in the UK. Wegovy is a once-weekly GLP-1 receptor agonist that may help reduce appetite and support weight loss when combined with diet and exercise changes. It's important to understand how semaglutide works, who may be eligible, and what to expect — including side effects and costs. This guide covers everything UK adults need to know about Wegovy and semaglutide for weight management.
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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.
How Semaglutide and Wegovy Work
Semaglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist — it activates a natural hormone pathway in your gut. When you take Wegovy, semaglutide:
- Signals to your brain that you feel full, reducing appetite and food cravings
- Slows how quickly food leaves your stomach, helping you feel satisfied longer after meals
- Helps regulate blood sugar levels and reduce overall hunger signals
Unlike Ozempic (which also contains semaglutide but is approved for type 2 diabetes management at lower doses), Wegovy is the licensed weight management version of semaglutide, reaching a maximum dose of 2.4 mg per week. Individual responses vary — some people experience significant appetite suppression, while others notice more modest effects. Use our free GLP-1 weight loss calculator to explore potential weight loss projections at different semaglutide doses.
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 Doses and Clinical Results
Wegovy semaglutide treatment starts at a low dose and increases gradually over 16 weeks. Your prescriber increases the dose every 4 weeks: 0.25 mg → 0.5 mg → 1 mg → 1.7 mg → 2.4 mg (maximum). The STEP-1 clinical trial showed that at the maximum 2.4 mg dose, participants lost an average of approximately 15% of their body weight over 68 weeks — though results vary significantly between individuals. This was achieved alongside a reduced-calorie diet and increased physical activity. Calculate your personal BMI and explore weight loss scenarios using our free weight loss calculator and BMI calculator to understand what results might mean for your health.
- 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's the difference between Wegovy and Ozempic?
Both contain semaglutide, but Ozempic is approved for type 2 diabetes (doses up to 2 mg) while Wegovy is specifically licensed for weight management (doses up to 2.4 mg). Ozempic is not licensed for weight loss in the UK — using it for that purpose is off-label. Wegovy is the correct prescription for weight management in UK adults.
How quickly will I lose weight on Wegovy semaglutide?
Clinical trials showed average weight loss of around 15% body weight over 68 weeks. However, results vary — some people lose more, others less. Weight loss typically becomes visible after 4–8 weeks of treatment. The NHS recommends losing weight at 0.5–1 kg per week for sustainable results. Individual outcomes depend on dose, diet, exercise, and metabolism.
What are the most common side effects of Wegovy semaglutide?
Common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain. These are usually most noticeable when starting treatment or increasing doses, and often improve over time. If side effects are severe or persistent, contact your prescriber. Serious side effects are rare but include severe stomach pain (possible pancreatitis) — seek immediate medical attention if this occurs.
Can I get Wegovy semaglutide on the NHS in the UK?
Wegovy access through the NHS varies by region and is typically available through specialist tier 3 weight management services following GP referral. Waiting times can be very long in many areas. Private online prescribing is available without NHS referral — you'll need an online clinical assessment from a UK-licensed prescriber and the prescription is dispensed by a GPhC-registered pharmacy.
Who is eligible for Wegovy semaglutide treatment?
In the UK, adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions (such as type 2 diabetes, high blood pressure, or sleep apnoea), may be eligible. Lower BMI thresholds apply for people of South Asian, Chinese, Black African, or Black Caribbean heritage. Pregnancy, breastfeeding, and certain medical conditions are contraindications. A prescriber will assess your individual eligibility.
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.