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 and How Does It Work?
Wegovy is a prescription-only weight management injection licensed in the UK for adults with obesity or overweight with weight-related health conditions. It contains semaglutide, a GLP-1 receptor agonist that activates natural hormone pathways to help reduce appetite and support feeling fuller after smaller meals. Clinical trials showed that Wegovy, alongside reduced-calorie diet and increased physical activity, may help participants lose an average of approximately 15% of their body weight — though individual results vary significantly. Access in the UK is available through NHS specialist weight management services or private online prescribing following a clinical assessment.
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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 UK Eligibility
Wegovy contains semaglutide, a GLP-1 receptor agonist that mimics glucagon-like peptide-1, a natural hormone released after eating. This hormone signals your brain that you are full, slows how quickly food leaves the stomach, and helps regulate blood sugar. Unlike Mounjaro, which is a dual GIP and GLP-1 agonist, Wegovy works through a single mechanism.
UK eligibility for Wegovy: You may be prescribed Wegovy if you have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² with at least one weight-related health condition such as type 2 diabetes, prediabetes, high blood pressure, abnormal cholesterol, sleep apnoea, or cardiovascular disease history. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply. A prescriber will assess your individual suitability following a clinical assessment. Use our free BMI calculator above to check where you stand, or the weight converter if you need to convert your weight between kg, stone, and pounds.
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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, Expected Results, and Side Effects
Wegovy is started at 0.25 mg weekly, escalating every 4 weeks to 0.5 mg, 1 mg, 1.7 mg, and finally 2.4 mg (the maximum maintenance dose). Based on STEP-1 clinical trial data, participants on 2.4 mg lost an average of approximately 15% of their body weight over 68 weeks alongside lifestyle changes — results vary individually. Our GLP-1 weight loss calculator can help you estimate potential outcomes at different doses. Common side effects include nausea, diarrhoea, constipation, and stomach pain, typically mild and temporary. Serious side effects are rare but include severe stomach pain (possible pancreatitis), gallbladder problems, or serious allergic reactions — seek immediate medical attention if these occur. Always discuss side effect management with your 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.
Is Wegovy the same as Ozempic?
Both contain semaglutide, but they are different products. Ozempic is approved for type 2 diabetes management with doses up to 2 mg. Wegovy is specifically licensed for weight management in the UK with doses up to 2.4 mg. Ozempic is not licensed for weight loss in the UK, so using it for weight management is off-label. Wegovy is the correct, licensed choice for weight management.
How do I access Wegovy in the UK?
Wegovy is available through two routes. NHS access is via referral to a specialist tier 3 weight management service from your GP — availability varies by region and waiting lists can be long. Private access is through a UK-licensed prescriber online, following a clinical assessment, dispensed by a GPhC-registered pharmacy. Both routes require a valid prescription; Wegovy is prescription-only and cannot be obtained without clinical assessment.
What's the difference between Wegovy and Mounjaro?
Wegovy (semaglutide) is a GLP-1 receptor agonist, while Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist. Wegovy has one mechanism; Mounjaro has two. In clinical trials, Mounjaro showed slightly higher average weight loss (up to 21% vs 15% for Wegovy), but results vary individually. Wegovy is a once-weekly injection; Mounjaro is also once-weekly. Your prescriber will assess which is more suitable for you.
How much weight can I expect to lose on Wegovy?
Clinical trials showed an average weight loss of approximately 15% of body weight on 2.4 mg Wegovy over 68 weeks, achieved alongside reduced-calorie diet and increased physical activity. Individual results vary significantly — some people lose more, some less. Weight loss depends on adherence, lifestyle changes, starting weight, and individual metabolism. Our weight loss calculator can provide a personalised estimate based on your circumstances.
What happens if I stop taking Wegovy?
If you stop Wegovy, weight loss effects gradually reduce over weeks as the medication leaves your system. Many people regain weight if they return to previous eating patterns, though some maintain losses through continued lifestyle changes. Wegovy is not a permanent supports — it is a tool to support weight loss alongside diet and exercise. Discuss any plans to stop with your prescriber, who can advise on the safest approach 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.