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- How GLP-1 medications work
- Mounjaro vs Wegovy compared
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- Side effects & solutions
- What to eat on treatment
- FAQs answered
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Mounjaro 7.5 mg vs Wegovy — UK Comparison Guide
If you're considering weight loss medication in the UK, you may have encountered both Mounjaro (tirzepatide) and Wegovy (semaglutide). Both are prescription-only GLP-1 medications available through NHS specialist services or private online prescribing. At the 7.5 mg dose, Mounjaro is in its mid-range escalation, while Wegovy would be at or near its maximum. Understanding how these medications differ — in mechanism, dosing, and clinical evidence — helps you and your GP or prescriber decide which might suit your situation. This guide compares them factually to help you have an informed discussion with your healthcare provider.
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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.
How Mounjaro 7.5 mg and Wegovy Differ: Mechanism and Dosing
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways in the body. The 7.5 mg dose is typically reached around week 9–12 of treatment. Wegovy (semaglutide) is a single GLP-1 receptor agonist that activates one pathway; the equivalent dose progression reaches 2.4 mg (maximum) by week 17 onwards.
- Mounjaro 7.5 mg: mid-range escalation; many patients continue escalating to 10, 12.5, or 15 mg
- Wegovy: at 7.5 mg equivalent roughly matches Wegovy 2.4 mg (maximum approved dose)
- Mechanism: Mounjaro's dual action may produce different appetite suppression and metabolic effects than Wegovy's single mechanism
- Frequency: Both are once-weekly injections via pre-filled pen
In clinical trials (SURMOUNT for Mounjaro, STEP for Wegovy), both showed significant weight loss, but the populations, trial durations, and measured outcomes differed, making direct comparison difficult.
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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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Clinical Trial Data and Individual Suitability
The SURMOUNT-1 trial (Mounjaro) showed average weight loss of approximately 19.5% at the 10 mg dose and 20.9% at 15 mg over 72 weeks. The STEP-1 trial (Wegovy) showed average weight loss of approximately 14.9% at the 2.4 mg maximum dose over 68 weeks. However, these are averages — individual results vary significantly based on adherence, diet, activity, genetics, and metabolic factors.
- Neither medication assures specific weight loss for any individual
- Both require a reduced-calorie diet and increased physical activity to be effective
- Your GP or prescriber will assess which is more suitable based on your health history, other medications, and personal circumstances
- Use our free GLP-1 weight loss calculator to understand potential outcomes at different doses
- 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 7.5 mg better than Wegovy?
No medication is universally "better" — suitability depends on individual factors. Mounjaro's dual mechanism may work differently than Wegovy's single mechanism, but trial data shows both are effective. Your prescriber will assess which is appropriate for you based on your health, other medications, and medical history.
Can I switch from Mounjaro to Wegovy?
Yes, but any medication switch must be managed by your prescriber. There is no official conversion chart between them; your prescriber will assess whether switching is appropriate and adjust doses accordingly. Do not stop one and start another without medical guidance.
How does the 7.5 mg Mounjaro dose compare to Wegovy dosing?
Mounjaro 7.5 mg is roughly equivalent to Wegovy 1.7 mg, not the maximum Wegovy dose (2.4 mg). Mounjaro dosing goes higher — up to 15 mg — so the comparison depends on which Wegovy dose you're considering. Your prescriber will advise the right dose for you.
Do I need NHS referral for Mounjaro or Wegovy in the UK?
For NHS access, you need referral to a tier 3 specialist weight management service. For private prescribing, you can access both through online consultation with a UK-licensed prescriber without NHS referral. Availability and waiting times vary significantly by region.
Which medication causes fewer side effects?
Both share common side effects including nausea, diarrhoea, and constipation. Individual tolerance varies greatly. Your prescriber will discuss potential side effects and monitor you during treatment. If one causes unacceptable side effects, switching may be considered.
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