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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Cheapest Mounjaro vs Wegovy — Which Costs Less in the UK?
When exploring weight loss injection options in the UK, cost is often a deciding factor alongside clinical effectiveness. Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only medicines available through private prescribing, but their pricing structures differ significantly. Understanding the cost comparison, how each works, and which might suit your individual needs requires looking beyond price alone. Both are licensed for weight management, work differently at a metabolic level, and require clinical assessment before prescription. This guide breaks down the facts to help you make an informed decision with your GP or prescriber.
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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 and Wegovy Work — And Why Cost Varies
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — meaning it activates two natural hormone pathways that regulate appetite and blood sugar. Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single pathway. This difference in mechanism can influence both efficacy and cost.
Clinical trial data shows:
- Mounjaro (SURMOUNT trial): participants lost an average of 15–21% of body weight over 72 weeks on the highest dose (15 mg weekly)
- Wegovy (STEP-1 trial): participants lost an average of approximately 15% of body weight over 68 weeks on the maximum dose (2.4 mg weekly)
Individual results vary significantly. Private prescription costs in the UK typically range from £129–£320 per month depending on dose and provider. Mounjaro may sometimes be priced differently to Wegovy due to different dosing schedules, but direct price comparison requires checking current provider rates — these change regularly.
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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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Cost, Dosing Schedule, and Practical Suitability
Both medications are once-weekly injections, making them equally convenient from a dosing perspective. However, starting doses differ: Mounjaro begins at 2.5 mg and escalates gradually to 15 mg maximum; Wegovy starts at 0.25 mg and escalates to 2.4 mg maximum. This means the cost trajectory differs — Mounjaro may involve longer escalation with different dose costs, while Wegovy reaches maximum dose faster.
Neither is routinely available on the NHS for weight loss (though rare exceptions exist through specialist services with very long waiting lists). Both require a clinical assessment confirming you meet eligibility criteria: BMI 30 or above, or BMI 27–29.9 with weight-related health conditions. Your prescriber will assess suitability based on your medical history, medications, and individual circumstances — not price alone. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses, and our BMI calculator to confirm your current category.
- 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?
Prices vary by provider and dose, changing regularly. Both typically cost £129–£320 monthly. Direct comparison requires checking current rates with prescribers. Cost alone shouldn't guide choice — clinical suitability is more important. Your prescriber assesses which is appropriate for you based on medical history and health conditions.
Why does Mounjaro cost more or less than Wegovy sometimes?
Pricing depends on manufacturer supply, provider markup, and demand. Mounjaro and Wegovy have different starting doses and escalation schedules, which affects total treatment cost over time. Ask your prescriber for current pricing for your specific dose to compare accurately.
Can I get Mounjaro or Wegovy free on the NHS in the UK?
Access on the NHS is extremely limited and varies by region. Both are available through specialist tier 3 weight management services in some areas, but waiting lists are typically very long. Most people access these medications privately through online prescribing services following a clinical assessment.
Which weight loss injection is more effective — Mounjaro or Wegovy?
Clinical trials show both are effective, with Mounjaro showing slightly higher average weight loss (15–21% vs 15%). However, individual results vary substantially. Effectiveness depends on your personal metabolism, adherence, lifestyle changes, and health conditions — not just the medication. Your prescriber will recommend based on your circumstances.
Do I need to choose the cheapest option if I'm eligible for both?
No. Your prescriber will assess clinical suitability based on your medical history, current medications, and health conditions — not cost. Both require a full clinical assessment. Discuss with your prescriber which is most appropriate for you, then compare current pricing once the medication is decided.
Ready to take control of your weight loss journey?
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