The UK's most complete GLP-1 guide
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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 vs Wegovy: Dose Conversion Chart
Comparing Mounjaro and Wegovy doses can help you understand the differences between these two prescription weight loss injections available in the UK. While both are once-weekly medicines, they use different mechanisms and dose ranges. This guide provides a factual conversion chart and explains how the doses compare, what clinical trials showed, and how your GP or prescriber will decide which is suitable for you. Individual results vary significantly, and prescription is based on personal health assessment.
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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.
Mounjaro and Wegovy Dose Comparison Chart
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both once-weekly injections for weight management in UK adults, but they work differently and use different dose ranges:
- Mounjaro: Starting dose 2.5 mg, escalating to maximum 15 mg per week. Dual GIP and GLP-1 receptor agonist.
- Wegovy: Starting dose 0.25 mg, escalating to maximum 2.4 mg per week. GLP-1 receptor agonist only.
Because they have different mechanisms and dose escalation schedules, there is no direct 1:1 conversion between doses. However, approximate clinical equivalence suggests Mounjaro 5 mg is roughly comparable to Wegovy 0.5 mg, Mounjaro 10 mg to Wegovy 1.7 mg, and Mounjaro 15 mg to Wegovy 2.4 mg. Any switch between medications must be managed by your prescriber — never change doses without clinical guidance. Use our GLP-1 weight loss calculator to explore potential outcomes at different doses.
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If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
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Why Doses Differ: SURMOUNT vs STEP Trial Data
The differences in dose ranges reflect how each medicine was tested and approved. Mounjaro was studied in the SURMOUNT-1 trial, where participants on the maximum 15 mg dose lost an average of approximately 20.9% of body weight over 72 weeks. Wegovy was studied in the STEP-1 trial, where the maximum 2.4 mg dose resulted in average weight loss of approximately 14.9% over 68 weeks. Both studies combined medication with reduced-calorie diet and increased physical activity. These are trial averages—individual results vary widely based on genetics, lifestyle, health conditions, and medication tolerance. Your GP will assess which medication and dose is most appropriate for your circumstances.
- 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.
Can I switch from Mounjaro to Wegovy or vice versa?
Yes, but only under prescriber guidance. Your GP or weight management specialist will determine the appropriate equivalent dose based on your response to treatment and health needs. Never self-switch between medications. Switching requires a new clinical assessment and prescription.
Why is Mounjaro's maximum dose (15 mg) higher than Wegovy's (2.4 mg)?
They are different medicines with different mechanisms. Mounjaro works on two hormone pathways (GIP and GLP-1), while Wegovy targets GLP-1 only. Higher doses reflect the dual mechanism and how each drug was tested in clinical trials. The numbers are not directly comparable.
Which injection shows better weight loss results — Mounjaro or Wegovy?
Clinical trials suggest Mounjaro may achieve slightly higher average weight loss (around 20.9% vs 14.9%), but individual results vary significantly. Some people respond better to one than the other. Your prescriber will recommend based on your personal health profile, not trial averages.
How long does it take to reach maximum dose with each?
Mounjaro: minimum 4 weeks on each dose level, reaching 15 mg around week 20+. Wegovy: slower escalation, reaching 2.4 mg around week 16–20. Your prescriber may adjust timing based on tolerance and side effects.
Can my GP prescribe these, or do I need a specialist?
NHS access typically requires referral to a tier 3 specialist weight management service. Private prescribing is available through GPhC-registered online prescribers following clinical assessment. Both routes require a valid UK prescription—these are prescription-only medicines, not available over-the-counter.
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