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: Dose Chart and Comparison
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both prescription-only weight loss injections licensed in the UK, but they work differently and use different dosing schedules. This guide compares the dose charts, mechanisms, and clinical trial data to help you understand the key differences. Both require a clinical assessment before prescription, and individual results vary significantly.
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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.
Dose Charts and Clinical Trial Comparison
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist with a once-weekly dosing schedule starting at 2.5 mg and titrating up to a maximum of 15 mg over 20 weeks. In the SURMOUNT-1 clinical trial, participants achieved average weight loss of approximately 15% at 5 mg, 19.5% at 10 mg, and 20.9% at 15 mg over 72 weeks.
Wegovy (semaglutide) is a GLP-1 receptor agonist only, also given once weekly, starting at 0.25 mg and titrating to a maximum of 2.4 mg over 16 weeks. In the STEP-1 clinical trial, participants achieved average weight loss of approximately 14.9% at the maximum 2.4 mg dose over 68 weeks.
The key difference is mechanism: Mounjaro activates two hormone pathways (GIP and GLP-1), while Wegovy activates GLP-1 only. This may explain why Mounjaro showed slightly higher average weight loss in trials, though individual responses vary considerably.
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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.
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Which Is Right for You? Prescriber Assessment
Both Mounjaro and Wegovy are prescribed based on individual eligibility assessment by a UK-licensed prescriber or NHS specialist service. Your prescriber will consider your BMI, weight-related health conditions, medical history, and any contraindications before recommending one over the other.
Use our free GLP-1 weight loss calculator to explore potential weight loss projections at different doses with either medication. Your BMI calculator result and personal health profile are far better guides than dose charts alone. Neither medication is "better" — suitability depends on your individual circumstances, prescriber preference, and availability through NHS or private routes.
Access in the UK is through NHS specialist tier 3 weight management services (often with waiting lists) or private online prescribing following a clinical consultation.
- 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.
What's the main difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP and GLP-1 receptor agonist (two hormone pathways), while Wegovy is a GLP-1 agonist only (one pathway). This difference in mechanism may explain why Mounjaro showed slightly higher average weight loss in clinical trials, though individual results vary.
How do the dosing schedules compare?
Both are once-weekly injections. Mounjaro starts at 2.5 mg and goes up to 15 mg over 20 weeks. Wegovy starts at 0.25 mg and reaches 2.4 mg over 16 weeks. The doses are not directly comparable between the two medications.
Which medication caused more weight loss in trials?
In clinical trials, Mounjaro showed average weight loss of approximately 20.9% at maximum dose, while Wegovy showed approximately 14.9%. However, both results were achieved with reduced-calorie diet and increased physical activity, and individual outcomes vary significantly.
Can I switch from Wegovy to Mounjaro or vice versa?
Any medication switch must be managed by your prescriber or NHS specialist service. There is no official established conversion between the two — your prescriber will assess the best approach for your individual situation.
How do I know which one to request from my GP?
Your GP or specialist prescriber assesses both medications based on your medical history, BMI, health conditions, and personal circumstances. Rather than requesting a specific medication, discuss your weight management goals with your GP and let the prescriber recommend the most suitable option for you.
Ready to take control of your weight loss journey?
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