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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 7.5mg vs Wegovy for Weight Loss
If you're considering a weekly weight loss injection in the UK, you've likely heard of both Mounjaro and Wegovy. At the 7.5mg Mounjaro dose—an escalation dose during treatment—how do these two prescription weight loss medications compare? This guide compares the mechanisms, clinical trial data, side effects, and suitability to help you understand the differences. Both require a UK prescription and clinical assessment from a licensed prescriber, 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.
How Mounjaro 7.5mg and Wegovy Work Differently
The key difference between these medications is their mechanism of action. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways simultaneously. This dual action may provide enhanced appetite suppression and support feeling fuller after meals. Wegovy (semaglutide) activates only the GLP-1 pathway—a single mechanism that still helps reduce appetite and food cravings.
In the SURMOUNT-1 clinical trial, Mounjaro 7.5mg (escalation dose) demonstrated average weight loss of approximately 19.5% of body weight over 72 weeks alongside a reduced-calorie diet and increased physical activity. Wegovy's STEP-1 trial showed average weight loss of approximately 14.9% at the maximum 2.4mg dose. However, these are trial averages—individual responses vary considerably, and direct comparisons should account for different patient populations and trial designs.
Both medications slow gastric emptying and work through the appetite centres in the brain, but Mounjaro's dual mechanism may produce stronger effects in some individuals. Your prescriber will assess which approach suits your health profile and medical history.
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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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Prescribing, Costs, and Practical Suitability
Both Mounjaro and Wegovy are prescription-only medicines in the UK available through NHS specialist weight management services or private online prescribing following clinical assessment. Mounjaro's dose titration schedule starts at 2.5mg and escalates weekly to 5mg, 7.5mg, 10mg, 12.5mg, and maximum 15mg. Wegovy escalates from 0.25mg to 2.4mg. The KwikPen auto-injector format is identical for both—once-weekly subcutaneous injection.
Access through the NHS varies by region and waiting times can be lengthy. Private prescribing is faster but involves costs typically ranging from £129–£320 monthly depending on dose. Your GP or a licensed prescriber will determine suitability based on BMI, weight-related health conditions, and contraindications. Use our free BMI calculator to check your starting point, and our GLP-1 weight loss calculator to explore potential outcomes at different doses of either medication.
- 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 7.5mg better than Wegovy for weight loss?
Clinical trial data suggests Mounjaro may produce slightly greater average weight loss (19.5% vs 14.9%), but individual results vary substantially. "Better" depends on your specific health profile, tolerability, and how your body responds. A prescriber will assess which is more suitable for you based on your medical history.
Can I switch from Wegovy to Mounjaro at 7.5mg?
Approximate dose equivalence places Mounjaro 7.5mg near Wegovy 1.7mg, not the maximum 2.4mg dose. Any switch between medications must be managed by your prescriber—there's no official conversion chart, and transitions require careful assessment and timing.
How long does it take to reach the 7.5mg Mounjaro dose?
Mounjaro's dose titration takes 8–12 weeks to reach 7.5mg, escalating weekly from 2.5mg. Each dose is typically held for one week before increasing. Your prescriber may adjust this schedule based on tolerability and side effects.
What are the main side effects of Mounjaro 7.5mg?
Very common side effects include nausea, diarrhoea, constipation, and stomach pain—typically mild to moderate during the first weeks and often improving with time. Serious side effects are rare but include pancreatitis symptoms (severe stomach pain) requiring immediate medical attention.
Is Mounjaro or Wegovy available on the NHS in the UK?
Both are licensed for NHS use through specialist tier 3 weight management services, though regional availability and waiting times vary significantly. Private access is available through GPhC-registered online pharmacies following a clinical assessment.
Ready to take control of your weight loss journey?
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