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: Cost and Effectiveness in the UK
If you're comparing Mounjaro and Wegovy for weight management, cost is often a key consideration alongside effectiveness. Both are prescription-only GLP-1 (or dual GIP/GLP-1) medications licensed in the UK, but they work differently, have different dose ranges, and vary in price depending on how you access them. This guide compares the two medications side-by-side so you can understand the key differences and what eligibility means for you. Our GLP-1 weight loss calculator can help you explore potential outcomes with each medication based on clinical trial data.
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Calculate Your BMI Instantly
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 and Wegovy Work Differently
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — it activates two natural hormone pathways simultaneously. This dual mechanism may give it a slight edge in appetite suppression and weight loss support.
Wegovy (semaglutide) is a GLP-1-only receptor agonist — it works on a single hormone pathway. Both are once-weekly injections delivered via pre-filled pens.
Clinical trial results (SURMOUNT vs STEP):
- Mounjaro at 15mg: average clinically studied weight loss over 72 weeks
- Wegovy at 2.4mg: average clinically studied weight loss over 68 weeks
- Results are averages — individual outcomes vary significantly
- Both require a reduced-calorie diet and increased physical activity to achieve results
Neither medication assures weight loss. Your prescriber will assess which is more suitable based on your individual health profile, medical history, and any other medications you take.
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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.
UK Cost, Access Routes, and Eligibility
NHS access: Both Mounjaro and Wegovy are available through NHS specialist tier 3/4 weight management services, but regional availability is very limited and waiting lists are often months to years.
Private prescription cost (approximate range):
- Mounjaro: £129–£320 per month depending on dose
- Wegovy: £180–£300 per month depending on dose
- Costs vary between pharmacies and prescribing providers
Eligibility (both medications): BMI 30+ or BMI 27+ with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea). A UK-licensed prescriber will assess your suitability following a clinical consultation. Use our BMI calculator above to check your personal BMI and understand where you fall on NHS eligibility thresholds.
- 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 always cheaper than Wegovy?
Not necessarily. Costs vary by dose, pharmacy, and prescribing provider. At lower doses, prices may be similar. At higher doses (Mounjaro 15mg vs Wegovy 2.4mg), Mounjaro can be more expensive. Always compare prices across providers and discuss cost with your prescriber — the "lowest price" option should not be the only deciding factor.
Which medication is more effective for weight loss?
Clinical trials show Mounjaro achieved slightly higher average weight loss (20.9% vs 14.9%), but individual results vary greatly. Some people respond better to one medication than the other. Your prescriber will recommend based on your health profile, not just average trial results. Both are effective when combined with lifestyle changes.
Can I switch between Mounjaro and Wegovy?
Yes, switching is possible and sometimes necessary if one medication isn't suitable or causes intolerable side effects. However, any switch must be managed by your prescriber. There is no official dose conversion chart — your prescriber will assess the appropriate starting dose if you switch medications.
How do I access Mounjaro or Wegovy on the NHS?
Request a referral to your NHS tier 3 or 4 specialist weight management service from your GP. However, NHS availability is very limited and varies significantly by region (ICB). Many areas have long waiting lists. Private prescription through an online UK-licensed prescriber is often faster but involves private cost.
What if I can't afford either medication privately?
Discuss options with your GP. Some areas have better NHS access than others. Community weight management programmes, dietary support, and physical activity services are available free through the NHS. Your GP can signpost you to available support in your area. Our progress tracker can help you log lifestyle changes alongside any prescribed treatment.
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.