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 and Ozempic — What You Need to Know
Ozempic is often discussed in weight loss conversations, but there's an important distinction in the UK: Ozempic is licensed for type 2 diabetes management, not weight management. Wegovy, which contains the same active ingredient (semaglutide), is the prescription-only medication specifically approved for weight management in UK adults. This guide explains the difference, how these medications work, and what the NHS says about prescription weight loss options. Calculate your BMI and eligibility using our free BMI calculator above to understand your personal health context.
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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.
Ozempic vs Wegovy — Understanding the Difference
Both Ozempic and Wegovy contain semaglutide, a GLP-1 receptor agonist. However, they are licensed for different purposes in the UK:
- Ozempic: Approved for type 2 diabetes management (doses up to 2 mg). It is not licensed for weight loss, though some people use it off-label for this purpose.
- Wegovy: Approved specifically for weight management in UK adults (doses up to 2.4 mg). This is the licensed weight loss version.
Using Ozempic for weight loss would be off-label prescribing, meaning it's outside its approved use. For weight management in the UK, Wegovy is the appropriate prescription-only option. Both require a clinical assessment before prescription. Our GLP-1 weight loss calculator can help you understand potential outcomes with licensed weight loss medication at different doses.
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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
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
How GLP-1 Weight Loss Works
GLP-1 receptor agonist medications like Wegovy work by mimicking a natural hormone in your body that helps regulate appetite and blood sugar. The medication may help reduce hunger, support feeling fuller after smaller meals, and slow how quickly food leaves your stomach. Clinical trials (the STEP studies) showed that participants taking Wegovy lost an average of approximately 15% of their body weight over 68 weeks, alongside a reduced-calorie diet and increased physical activity.
Individual results vary significantly depending on dose, lifestyle changes, and personal metabolism. Prescription weight loss is typically used as part of a broader weight management strategy alongside diet and exercise, not as a standalone solution. Track your progress with our free progress tracker as you work towards your health goals.
- 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 Ozempic used for weight loss in the UK?
Ozempic is licensed for type 2 diabetes management, not weight loss. Wegovy, which contains the same active ingredient (semaglutide), is the prescription-only medication specifically approved for weight management in UK adults. Using Ozempic for weight loss would be off-label prescribing. Always speak to your GP or a licensed prescriber about which medication is appropriate for you.
How much weight can I expect to lose on Wegovy?
In the STEP-1 clinical trial, participants taking Wegovy lost an average of approximately 15% of their body weight over 68 weeks, alongside a reduced-calorie diet and increased physical activity. However, individual results vary significantly based on dose, adherence, lifestyle changes, and personal metabolism. Your GP can provide personalised expectations.
Is Wegovy available on the NHS?
Wegovy is available through NHS specialist weight management services (tier 3 services), though access varies by region and availability can be limited. Private prescription is also available through UK-licensed online prescribers following a clinical assessment. NHS referral typically comes through your GP to specialist services.
What's the difference between a GLP-1 and a GIP/GLP-1 medication?
GLP-1 medications (like Wegovy) activate one hormone pathway. GIP/GLP-1 medications (like Mounjaro) activate two pathways simultaneously. Both are prescription-only weight management options. Mounjaro may show slightly higher average weight loss in trials, but individual results vary. Your prescriber will advise which is most suitable based on your health.
What are the main side effects of semaglutide?
Common side effects include nausea, diarrhoea, constipation, and stomach pain. These often improve as your body adjusts. More serious but rare side effects include pancreatitis and gallbladder problems. Always report any new or persistent symptoms to your GP. Use our weight converter tool to check healthy weight ranges alongside medical guidance about any medication you're considering.
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.