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- 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 Cost in the UK — Comparison with Wegovy
Finding the cheapest Mounjaro 15mg in the UK requires understanding both NHS and private options, as pricing varies significantly. Mounjaro (tirzepatide) is a prescription-only weight loss injection available through NHS specialist services or private prescribers following clinical assessment. This guide compares Mounjaro 15mg costs with Wegovy, explains how the two medications work differently, and helps you understand your options for accessing prescription weight loss treatment 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.
How Mounjaro 15mg and Wegovy Compare: Mechanism, Trials, and Pricing
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — meaning it activates two hormone pathways, whereas Wegovy (semaglutide) activates only the GLP-1 pathway. This dual mechanism is what makes Mounjaro mechanistically different from other weight loss injections available in the UK.
In the SURMOUNT-1 clinical trial, Mounjaro 15mg showed average weight loss of approximately 20.9% of body weight over 72 weeks, compared to STEP-1 trial data for Wegovy 2.4mg showing approximately 14.9% average weight loss over 68 weeks. However, individual results vary significantly, and both medications require a reduced-calorie diet and increased physical activity to be effective.
- Mounjaro 15mg: Maximum dose, once-weekly KwikPen injection, approximately £200–£280 per month private (cost varies by provider)
- Wegovy 2.4mg: Maximum dose, once-weekly pre-filled pen, approximately £180–£250 per month private (cost varies by provider)
Both are prescription-only medicines in the UK and require clinical assessment before being prescribed. Pricing depends on your chosen provider and whether you access through NHS specialist services (waiting lists vary by region) or private prescribing (typically faster access, out-of-pocket costs).
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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.
Individual Suitability and How to Access the Cheapest Option
The "cheapest" option depends on your eligibility, location, and preference for NHS vs private access. On the NHS: Access is free once prescribed through specialist tier 3 weight management services, but waiting lists can be months to years depending on your Integrated Care Board (ICB) region. Privately: Compare GPhC-registered online prescribers — costs range from £129–£320 per month depending on dose and provider.
A prescriber will assess whether Mounjaro or Wegovy is more suitable based on your individual health, medical history, and personal circumstances. Try our free GLP-1 weight loss calculator above to explore projected outcomes at different doses, then discuss your options with your GP or a licensed prescriber. Use the BMI calculator on this page to check where you stand relative to NHS eligibility thresholds (BMI 30+, or 27+ with weight-related conditions).
- 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 cheaper than Wegovy in the UK?
Private pricing is similar — approximately £200–£280/month for Mounjaro 15mg vs £180–£250/month for Wegovy 2.4mg, depending on provider. NHS access is free but involves waiting lists. Actual cost depends on which prescriber you use and your region.
How much weight did people lose on Mounjaro 15mg in clinical trials?
In the SURMOUNT-1 trial, Mounjaro 15mg showed average weight loss of 20.9% of body weight over 72 weeks. Individual results vary significantly. This was achieved alongside a reduced-calorie diet and increased physical activity.
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy is a GLP-1 agonist only. The SURMOUNT trial showed higher average weight loss for Mounjaro (20.9%) vs STEP trial for Wegovy (14.9%), but a prescriber will assess which suits your individual health circumstances.
Can I get Mounjaro 15mg on the NHS in the UK?
Yes, Mounjaro is approved by NICE for NHS specialist weight management services. Access requires GP referral to tier 3 services. Availability and waiting times vary significantly by region. Private access is available through GPhC-registered prescribers without NHS referral.
How do I find the cheapest Mounjaro 15mg prescription in the UK?
Compare private GPhC-registered online prescribers, as costs vary. Alternatively, ask your GP about NHS specialist weight management services in your area — NHS access is free but waiting lists apply. A prescriber will assess your eligibility and recommend the most suitable medication.
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.