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 Does Ozempic Do For Weight Loss?
Ozempic contains semaglutide but is not licensed for weight loss in the UK — it's approved for type 2 diabetes management only. However, a higher-dose semaglutide injection called Wegovy is specifically licensed for weight management in UK adults. Both contain the same active ingredient but serve different purposes. This guide explains how semaglutide works, why Ozempic isn't prescribed for weight loss, and what prescription weight loss options are actually available to you through the NHS or private prescribing.
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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 Semaglutide Works For Weight Management
Semaglutide is a GLP-1 receptor agonist — it mimics a natural hormone your gut produces after eating. When you take semaglutide, it signals to your brain that you're fuller, reducing appetite and food cravings. It also slows how quickly food leaves your stomach, helping you feel satisfied after smaller meals, and improves how your body handles blood sugar.
- In clinical trials (STEP-1), participants on semaglutide 2.4 mg lost an average of approximately 14.9% of their body weight over 68 weeks
- Results varied — some lost more, some less — and were achieved alongside a reduced-calorie diet and increased physical activity
- Weight loss continued as long as the medication was taken; stopping it typically led to weight regain
This mechanism makes semaglutide effective for weight management in prescription weight loss injections, which is why Wegovy (the licensed weight loss version) is available in the UK for eligible adults.
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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.
Ozempic vs Wegovy — Why The Difference Matters
Both Ozempic and Wegovy contain semaglutide, but they are different medicines:
- Ozempic: Approved for type 2 diabetes (doses up to 2 mg weekly) — NOT licensed for weight loss in the UK
- Wegovy: Approved specifically for weight management (doses up to 2.4 mg weekly) — this is the licensed weight loss injection
Using Ozempic for weight loss would be off-label prescribing, which is not standard practice. If you're interested in prescription weight loss options, your GP can refer you to NHS specialist weight management services, or you can consult a private prescriber about Wegovy or other licensed weight management treatments. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses.
- 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 ever prescribed for weight loss in the UK?
No — Ozempic is not licensed for weight loss in the UK. It's approved only for type 2 diabetes management. Wegovy is the licensed semaglutide injection for weight management. Any off-label use of Ozempic for weight loss would be non-standard. Always consult your GP or a licensed prescriber about appropriate weight management options.
What's the difference between Ozempic and Wegovy?
Both contain semaglutide but have different licensed uses and doses. Ozempic is for diabetes (up to 2 mg weekly). Wegovy is for weight management (up to 2.4 mg weekly). Wegovy is the prescription weight loss version available in the UK for eligible adults with a BMI of 30 or above, or 27 or above with weight-related health conditions.
How much weight can you lose with semaglutide?
In clinical trials, semaglutide 2.4 mg helped participants lose an average of approximately 15% of their body weight — though individual results vary significantly. Weight loss was achieved alongside dietary changes and increased physical activity. Results depend on dose, adherence, lifestyle, and individual factors.
How do I access weight loss injections in the UK?
Through two routes: NHS specialist tier 3 weight management services (requires GP referral, availability varies by region) or private online prescribing (following clinical assessment with a UK-licensed prescriber). Both routes require a prescription — these are prescription-only medicines.
Does weight loss continue indefinitely with semaglutide?
Weight loss typically plateaus after several months on a stable dose. If you stop taking semaglutide, weight tends to return over time. This is why ongoing use (or lifestyle maintenance) is important for sustained weight management. Your prescriber will advise on treatment duration for your individual situation.
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.