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 vs Wegovy — Understanding Equivalent Doses
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both prescription-only weight management injections available in the UK, but they work differently and have different maximum doses. Mounjaro reaches a maximum of 15mg weekly, whilst Wegovy's maximum is 2.4mg weekly — these are not directly interchangeable doses. Understanding how these medications compare, what they cost, and how to access them can help you make an informed decision about your weight management 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.
How Mounjaro and Wegovy Compare — Dosing and Mechanism
Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways, whilst Wegovy is a single GLP-1 receptor agonist. This fundamental difference in mechanism means their doses cannot be directly compared — a higher Mounjaro dose does not necessarily produce the same effect as a higher Wegovy dose.
Approximate dose equivalence based on clinical trial data suggests: Mounjaro 5mg is roughly equivalent to Wegovy 0.5mg, Mounjaro 10mg to Wegovy 1.7mg, and Mounjaro 15mg to Wegovy 2.4mg. However, these are approximate comparisons only — individual response varies significantly. In clinical trials, Mounjaro users lost an average of 20.9% body weight at the 15mg dose, whilst Wegovy users lost approximately 14.9% at the 2.4mg maximum dose. Both medications work alongside reduced-calorie diet and increased physical activity. Any switch between these medications must be managed by your prescriber.
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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
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Cost and Access — NHS vs Private Routes in the UK
NHS access: Both medications are NICE-approved and available through NHS specialist tier 3 weight management services, but availability is limited by region and waiting lists can be substantial — often 6–18 months depending on your area. Your GP can refer you to local specialist services.
Private access: Both Mounjaro and Wegovy are available through private online prescribing services. Following an online clinical assessment with a UK-licensed prescriber, a prescription can be issued if clinically appropriate. Typical costs range from £129–£320 per month depending on the dose and provider. You'll need to be assessed for eligibility — usually requiring a BMI of 30 or above, or 27+ with weight-related health conditions. Use our free GLP-1 weight loss calculator to explore potential outcomes, and our BMI calculator to check your current category.
NHS access: Both medications are NICE-approved and available through NHS specialist tier 3 weight management services, but availability is limited by region and waiting lists can be substantial — often 6–18 months depending on your area. Your GP can refer you to local specialist services.
Private access: Both Mounjaro and Wegovy are available through private online prescribing services. Following an online clinical assessment with a UK-licensed prescriber, a prescription can be issued if clinically appropriate. Typical costs range from £129–£320 per month depending on the dose and provider. You'll need to be assessed for eligibility — usually requiring a BMI of 30 or above, or 27+ with weight-related health conditions. Use our free GLP-1 weight loss calculator to explore potential outcomes, and our BMI calculator to check 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.
Which is better — Mounjaro 15mg or Wegovy 2.4mg?
Neither is objectively "better" — clinical trials show Mounjaro produced slightly higher average weight loss (20.9% vs 14.9%), but individual results vary significantly. Choice depends on individual response, side effect tolerance, and prescriber recommendation. Both require prescription and clinical assessment.
Can I switch from Wegovy to Mounjaro?
Yes, but only under medical guidance. Your prescriber will manage any medication switch, likely with a transition period. Direct switching is not recommended — your prescriber will advise the safest approach based on your health.
How much does Wegovy cost privately in the UK?
Private Wegovy costs typically range from £129–£250 per month, depending on dose and provider. Prices vary as Wegovy has become more widely available. Always check current pricing with registered prescribers.
What does "equivalent dose" mean for Mounjaro and Wegovy?
Approximate equivalence is based on clinical trial weight loss data, not direct pharmacological comparison. Mounjaro 15mg ≈ Wegovy 2.4mg in terms of rough weight loss outcomes, but the medications work through different mechanisms — response will vary between individuals.
Can I get Mounjaro or Wegovy on the NHS quickly?
NHS availability is limited. You'll be referred to specialist tier 3 weight management services by your GP, but waiting times vary by region — typically 6–18 months. Private online prescribing routes are faster (assessments usually within days to weeks).
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.