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 15mg Prices and How It Compares to Wegovy
Mounjaro (tirzepatide) at the 15mg maximum dose and Wegovy (semaglutide) at 2.4mg are the two most prescribed GLP-1 weight loss injections in the UK. If you're comparing these medications, cost is likely a key consideration alongside effectiveness and suitability. Both are prescription-only medicines requiring clinical assessment, and prices vary depending on whether you access them through the NHS or privately. This guide explains the pricing, clinical evidence, and key differences to help you understand your options.
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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 Trial Results and How They Compare
Mounjaro (tirzepatide) at 15mg showed average weight loss of approximately 20.9% of body weight over 72 weeks in the SURMOUNT-1 clinical trial, alongside a reduced-calorie diet and increased physical activity. Wegovy (semaglutide) at 2.4mg showed average weight loss of approximately 14.9% of body weight over 68 weeks in the STEP-1 trial under similar lifestyle conditions.
- Mounjaro uses a dual GIP and GLP-1 receptor agonist mechanism (activates two hormone pathways)
- Wegovy uses a single GLP-1 receptor agonist mechanism (activates one hormone pathway)
- Both medications work alongside diet and exercise — results vary significantly between individuals
- Clinical trial data is averaged across many participants; your personal outcome may differ
Use our free GLP-1 weight loss calculator to project potential outcomes at different doses of either medication.
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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, Access Routes, and Prescriber Assessment
Both Mounjaro and Wegovy are available in the UK through NHS specialist weight management services (tier 3) and through private GPhC-registered online prescribing. NHS access varies significantly by region and often involves waiting lists of several months. Private costs typically range from £129–£320 per month depending on dose and provider.
- At maximum dose (Mounjaro 15mg or Wegovy 2.4mg), private pricing is usually at the higher end of this range
- A UK-licensed prescriber must assess your eligibility based on BMI, health conditions, and suitability
- Prescription is required regardless of route — neither medication is available over-the-counter
Your GP can advise on NHS referral options, or you can seek a private online clinical assessment to access either medication more quickly.
- 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 15mg more expensive than Wegovy 2.4mg in the UK?
Pricing varies by private provider, but both medications at maximum dose typically cost between £250–£320 per month privately. NHS costs are covered but availability depends on your region and tier 3 service capacity. Direct price comparison is difficult because different providers charge different amounts. Always check current pricing with your chosen provider.
Which medication causes more weight loss — Mounjaro or Wegovy?
Clinical trials showed Mounjaro 15mg resulted in slightly higher average weight loss (20.9%) compared to Wegovy 2.4mg (14.9%). However, individual results vary significantly. Some people respond better to one medication than the other. Your prescriber will assess which is more suitable for you based on your health profile and medical history.
Can I switch from Mounjaro to Wegovy or vice versa?
Yes, switching is possible, but it must be managed by your prescriber. There is no official established conversion formula — approximate equivalences exist (Mounjaro 5mg ≈ Wegovy 0.5mg, Mounjaro 15mg ≈ Wegovy 2.4mg), but these are clinical guidance only. Any switch requires a new assessment and prescription adjustment.
How do I know if I'm eligible for Mounjaro or Wegovy on the NHS?
NHS eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, cardiovascular disease, sleep apnoea). For South Asian, Chinese, Black African, or Black Caribbean adults, lower thresholds may apply. Your GP can assess your eligibility for tier 3 referral.
What are the main side effects of both medications?
Both cause similar common side effects: nausea, diarrhoea, vomiting, constipation, and stomach pain, especially during dose titration. These often decrease over time. Mounjaro and Wegovy also carry rare serious risks including pancreatitis and gallbladder problems. Your prescriber will discuss all risks and monitor you during treatment.
Ready to take control of your weight loss journey?
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