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 Diet Plan UK vs Wegovy โ What's the Difference?
If you're considering prescription weight loss injections in the UK, you've likely heard of both Mounjaro and Wegovy. While both are licensed for weight management in UK adults, they work differently and may suit different individuals. Understanding how they compare โ from their mechanism of action to trial results and dosing โ helps you make an informed decision with your GP or prescriber. This guide breaks down the key differences between Mounjaro (tirzepatide) and Wegovy (semaglutide) to support your weight loss journey.
10,000+ calculations today ยท NHS-aligned thresholds ยท 100% free
Calculate Your BMI Instantly
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/mยฒ).
While BMI isn't a perfect measure โ it doesn't account for muscle mass, bone density, or fat distribution โ 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 โ 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 vs Wegovy โ Mechanism, Doses, and Clinical Trial Results
How they work: Mounjaro is a dual GIP and GLP-1 receptor agonist โ it activates two natural hormone pathways to regulate appetite and food cravings. Wegovy is a GLP-1 receptor agonist only, working through a single mechanism. This dual action in Mounjaro may be why some individuals report different results, though individual response varies significantly.
Starting doses and titration: Mounjaro starts at 2.5 mg weekly, escalating to a maximum of 15 mg. Wegovy begins at 0.25 mg, increasing to 2.4 mg maximum. Both require at least 4 weeks on each dose before increasing, making Mounjaro's titration schedule longer (21+ weeks to reach maximum vs 17 weeks for Wegovy).
Clinical trial data: SURMOUNT-1 (Mounjaro) showed approximately 20.9% average body weight loss at 15 mg over 72 weeks. STEP-1 (Wegovy) showed approximately 14.9% average weight loss at 2.4 mg over 68 weeks. Important: These are clinical trial averages alongside reduced-calorie diet and increased physical activity โ individual results vary, and weight loss is not assured.
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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 โ 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 โ completely free.
Which Injection Suits You โ Individual Suitability and Prescriber Assessment
Both Mounjaro and Wegovy require the same eligibility assessment. You may be eligible if you have a BMI of 30 kg/mยฒ or above, or 27โ29.9 kg/mยฒ with a weight-related health condition (such as type 2 diabetes, high blood pressure, or cardiovascular disease). If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply.
Your prescriber will assess which medication is appropriate based on your individual health profile, previous medication responses, and personal preferences. Some individuals tolerate one better than the other โ side effects like nausea, constipation, or injection site reactions vary person to person. There is no one-size-fits-all answer; your GP or licensed prescriber will guide you based on your circumstances. Use our free GLP-1 weight loss calculator to explore potential outcomes, and our BMI calculator to understand your current health context.
- 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 โ 5mg โ 7.5mg โ 10mg โ 12.5mg โ 15mg
- GLP-1 receptor agonist
- Up to 15โ17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg โ 0.5mg โ 1mg โ 1.7mg โ 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 | 15โ22.5% | 12โ17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20โ32 weeks | 16โ20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | ยฃ150โยฃ250/month | ยฃ150โยฃ300/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 โ 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 better than Wegovy for weight loss?
Clinical trials show different average results โ Mounjaro showed approximately clinically studied weight loss versus Wegovy's 14.9% โ but individual outcomes vary significantly. "Better" depends on your personal health profile, how your body responds, and side effect tolerance. Your prescriber will assess which is more suitable for you.
Can I switch from Wegovy to Mounjaro or vice versa?
Yes, switches between medications are possible and managed by your prescriber. There is no official conversion chart, but approximate equivalences exist (for example, Wegovy 1.7 mg is roughly equivalent to Mounjaro 10 mg). Any switch requires medical supervision and reassessment.
How long does it take to reach the maximum dose with each injection?
Mounjaro takes approximately 21+ weeks to reach the maximum 15 mg dose (4 weeks at each dose: 2.5, 5, 7.5, 10, 12.5, 15 mg). Wegovy takes approximately 17 weeks to reach 2.4 mg (0.25, 0.5, 1, 1.7, 2.4 mg). Your prescriber may adjust the schedule based on side effects or response.
Do I need a special diet plan while taking Mounjaro or Wegovy?
Both medications work alongside a reduced-calorie diet and increased physical activity โ they are not replacements for lifestyle changes. Your prescriber or a registered dietitian can advise on a suitable diet plan. The medication helps you feel fuller after smaller meals, but you still need to make mindful food choices and stay physically active.
How do I access Mounjaro or Wegovy in the UK?
Both are available through NHS specialist weight management services (Tier 3) following GP referral, though availability and waiting lists vary significantly by region. Both are also available through private online prescribing with a UK-licensed prescriber, dispensed by a GPhC-registered pharmacy.
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.