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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Is Wegovy Better Than Mounjaro for Weight Loss?
Whether Wegovy or Mounjaro is "better" depends on your individual health profile, not on one being universally superior. Both are prescription-only weight management injections licensed in the UK, but they work differently and deliver different average results in clinical trials. This guide compares them factually so you can understand what your GP or prescriber might discuss with you.
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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 Wegovy and Mounjaro Differ
Mechanism: Wegovy (semaglutide) is a GLP-1 receptor agonist — it activates one hormone pathway. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — it activates two pathways. This dual action may explain why Mounjaro achieved higher average weight loss in clinical trials.
Clinical trial results: In the STEP-1 trial, Wegovy at maximum dose (2.4 mg) delivered approximately 14.9% average body weight loss over 68 weeks. In the SURMOUNT-1 trial, Mounjaro at 15 mg delivered approximately 20.9% average body weight loss over 72 weeks. However, individual results vary significantly — these are averages, not assures.
Dosing: Wegovy escalates from 0.25 mg to a maximum of 2.4 mg over 16 weeks. Mounjaro escalates from 2.5 mg to a maximum of 15 mg over 20 weeks. Both are once-weekly injections.
- Mounjaro offers more dose flexibility across a wider range
- Wegovy reaches maximum dose faster
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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.
What Your Prescriber Will Consider
Neither medication is inherently "better" — suitability depends on your health history, other medications, and individual response. Your GP or a licensed prescriber will assess factors including your BMI, weight-related health conditions (such as type 2 diabetes or high blood pressure), tolerance to side effects, and any contraindications.
Both require a reduced-calorie diet and increased physical activity to work effectively. Use our free GLP-1 weight loss calculator to explore projected outcomes at different doses, and our BMI calculator to understand your starting point. Access in the UK is through NHS specialist weight management services or private prescribing following a clinical assessment.
- 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.
Does Mounjaro always deliver more weight loss than Wegovy?
Clinical trial data shows Mounjaro had higher average results (20.9% vs 14.9% body weight), but individual outcomes vary widely. Some people respond better to one than the other. Your prescriber will consider your personal health factors when recommending which might suit you.
Can I switch from Wegovy to Mounjaro in the UK?
Yes, switching is possible but must be managed by your prescriber. There is no official conversion chart — approximate equivalences exist (e.g., Wegovy 2.4 mg is roughly equivalent to Mounjaro 10–15 mg), but any switch requires a new assessment and prescription.
Which has fewer side effects, Wegovy or Mounjaro?
Both share similar common side effects (nausea, diarrhoea, constipation, stomach pain). Frequency and severity vary between individuals. Side effects typically improve as your body adjusts. Your prescriber can discuss which might suit your tolerance profile better.
Is Mounjaro available on the NHS like Wegovy?
Both are approved for use within NHS specialist weight management services (tier 3), but access and availability vary significantly by region and ICB. Waiting lists can be long. Private access is available through GPhC-registered online prescribing for both.
Why would a GP prescribe Wegovy instead of Mounjaro?
Reasons include clinical suitability for your health profile, medication interactions, tolerability, availability, cost (if private), or established effectiveness for you. Wegovy's faster dose escalation may suit some patients better. Your prescriber will explain their recommendation.
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.