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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Wegovy vs Ozempic for Weight Loss — Key Differences
Both Wegovy and Ozempic contain the same active ingredient: semaglutide. However, they are licensed for different purposes in the UK. Wegovy is the prescription-only weight management injection licensed specifically for weight loss, while Ozempic is approved for type 2 diabetes treatment. Using Ozempic for weight loss would be off-label use and is not recommended. This guide explains the critical differences between these two medications and why Wegovy is the appropriate choice for weight management in the UK.
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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.
Understanding the Difference Between Wegovy and Ozempic
Both medications contain semaglutide, a GLP-1 receptor agonist that activates natural appetite-regulating hormones. However, they differ fundamentally in their licensed purpose, dosing, and regulatory status:
- Wegovy: Licensed in the UK specifically for weight management in adults with a BMI of 30 or above (or 27+ with weight-related health conditions). It is a weekly weight loss injection designed to support reduced appetite and sustained weight loss.
- Ozempic: Licensed in the UK for managing type 2 diabetes. It is not approved for weight loss, and using it for weight management would be off-label prescribing. Maximum diabetes dose is 2 mg weekly, lower than Wegovy's maximum.
The key distinction: Wegovy is licensed for weight loss; Ozempic is licensed for diabetes management. Using one medication for an unlicensed indication should only occur under specialist medical guidance, and this is not standard practice for weight management in the UK.
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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.
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Wegovy Dosing, Results, and How to Access in the UK
Wegovy is a once-weekly semaglutide weight loss injection available in doses from 0.25 mg up to 2.4 mg. Clinical trials (the STEP studies) showed that participants on 2.4 mg lost approximately 14.9% of their body weight on average over 68 weeks, alongside a reduced-calorie diet and increased physical activity. Individual results vary significantly. Try our GLP-1 weight loss calculator to estimate potential weight loss at different doses. In the UK, Wegovy is available through NHS specialist weight management services (with potential waiting lists) or via private prescription following an online clinical assessment. Your GP or a licensed prescriber will assess whether Wegovy is appropriate for you based on your individual health and eligibility.
- 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.
Can you use Ozempic for weight loss in the UK?
Ozempic is licensed for type 2 diabetes, not weight loss. Using it for weight loss would be off-label and is not standard practice. Wegovy is the licensed weight loss version of semaglutide in the UK. Only a specialist prescriber would consider off-label use, and this is rare.
What's the difference between Wegovy and Ozempic doses?
Ozempic maximum dose is 2 mg weekly (for diabetes). Wegovy maximum is 2.4 mg weekly (for weight loss). Although Wegovy's top dose is slightly higher, the main difference is licensed purpose, not just dose strength. Each medication is formulated for its specific use.
Is Wegovy available on the NHS in the UK?
Yes, Wegovy is available through NHS specialist tier 3/4 weight management services, but availability varies by region and waiting lists can be long. Private prescription is also available following an online clinical assessment. Your GP can refer you to specialist services or you can access private prescribing directly.
How much weight can you lose with Wegovy?
Clinical trials showed average weight loss of around 14.9% of body weight at the maximum dose (2.4 mg). This equals roughly 10–15 kg for many people, but individual results vary significantly. Weight loss depends on dose, diet, exercise, genetics, and personal metabolism.
Do Wegovy and Ozempic have the same side effects?
Both contain semaglutide, so side effects are similar: nausea, diarrhoea, vomiting, constipation, and stomach pain are most common. Serious side effects like pancreatitis or gallbladder issues are rare but possible. Your prescriber will discuss all risks before starting treatment.
Ready to take control of your weight loss journey?
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