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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Mounjaro vs Wegovy: UK Price and Cost Comparison
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management injections available in the UK, but they differ significantly in cost, mechanism, and clinical evidence. This guide compares pricing, access routes, and key differences to help you understand your options. Prices vary depending on whether you're accessing medication through the NHS or private prescribers, and both require a clinical assessment before being prescribed. Individual suitability is determined by a licensed healthcare professional based on your personal health profile.
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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.
Clinical Evidence and Mechanism: SURMOUNT vs STEP Trials
Mounjaro (tirzepatide) uses a dual GIP and GLP-1 receptor agonist mechanism, meaning it activates two natural hormone pathways to help regulate appetite. The SURMOUNT-1 clinical trial showed an average weight loss of approximately 15% to 20.9% of body weight depending on dose, when used alongside a reduced-calorie diet and increased physical activity. Wegovy (semaglutide) works as a GLP-1 receptor agonist only, activating a single hormone pathway. The STEP-1 clinical trial demonstrated an average weight loss of approximately 14.9% of body weight at the maximum dose. Both are prescription-only and require a clinical assessment. Neither medication assures specific weight loss outcomes — individual results vary significantly. The choice between them depends on prescriber assessment, your medical history, and individual suitability rather than price alone.
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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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UK Pricing and Access Routes Compared
Private access pricing (approximate): Mounjaro costs roughly £129–£320 per month depending on dose, while Wegovy typically costs £150–£300 per month. Prices vary between private prescribers and pharmacies. NHS access: Both medications are available through NHS specialist weight management services (tier 3), but availability and waiting times vary significantly by region. Your GP can refer you to a specialist service, though access is not assured and lists can be lengthy in many areas. Use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses, and discuss both options with your prescriber to determine which is most suitable for your individual circumstances and health needs.
- 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 Mounjaro cheaper than Wegovy in the UK?
Pricing is similar, with both typically ranging £129–£320 per month privately depending on dose and provider. Exact costs vary by pharmacy and prescriber. NHS access through specialist services means no direct cost to you, but availability is limited and varies by region. Your prescriber will assess clinical suitability rather than cost.
What's the main difference between Mounjaro and Wegovy?
Mounjaro uses a dual GIP and GLP-1 mechanism, while Wegovy uses GLP-1 only. SURMOUNT trial data showed Mounjaro achieved average weight loss of 15–20.9%, while STEP trial data showed Wegovy around 14.9%. Both require clinical assessment and individual results vary significantly.
Can I get either medication free on the NHS?
Both are available through NHS specialist weight management services (tier 3), but access is limited and varies by region. Your GP can refer you for assessment. Waiting times can be lengthy. Private access bypasses NHS waiting lists but involves direct cost to you.
Which injection is given more often — Mounjaro or Wegovy?
Both are once-weekly injections. Mounjaro uses a KwikPen and starts at 2.5 mg, escalating to 15 mg maximum. Wegovy starts at 0.25 mg and escalates to 2.4 mg maximum. Dose titration schedules differ, which your prescriber will manage.
How do I decide which medication is right for me?
A licensed prescriber will assess your individual health history, medical conditions, current medications, and suitability. Both require a clinical assessment before prescription. Your GP or private prescriber can discuss which option is most appropriate for your circumstances and any relevant eligibility criteria.
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.