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 Max Dosage vs Wegovy — What's the Difference?
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both prescription-only weight management injections licensed in the UK, but they work differently and have different maximum doses. Understanding the key differences — including mechanism of action, dose titration, and clinical trial outcomes — can help you understand which might be suitable if you're considering weight loss treatment. Both require a clinical assessment and prescription from a UK-licensed healthcare professional. This guide compares the two directly using NHS and clinical trial evidence.
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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/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 and Wegovy Differ — Mechanism and Maximum Dosage
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways in the body. The maximum dose is 15 mg once weekly, delivered via a KwikPen. In the SURMOUNT clinical trials, participants achieved an average weight loss of approximately 15–21% of their body weight at maximum dose (15 mg) alongside a reduced-calorie diet and increased physical activity.
Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single hormone pathway. The maximum dose is 2.4 mg once weekly, delivered via an auto-injection pen. In the STEP clinical trials, participants achieved an average weight loss of approximately 14.9% of body weight at maximum dose (2.4 mg) under the same lifestyle conditions.
- Dose escalation: Mounjaro escalates over 20 weeks (starting 2.5 mg); Wegovy escalates over 16 weeks (starting 0.25 mg)
- Individual results vary — maximum dose may not be necessary or suitable for everyone
- Both are prescription-only and require clinical assessment before prescribing
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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.
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Which Is Right for You? Prescriber Assessment and Suitability
Neither medication is "better" — suitability depends on individual health factors, medical history, and prescriber judgment. Your GP or a licensed prescriber will assess you based on BMI, weight-related health conditions (such as type 2 diabetes, high blood pressure, or sleep apnoea), and any contraindications. Both medications require a UK prescription and clinical assessment. Access in the UK is through NHS specialist tier 3/4 weight management services (subject to regional availability and waiting lists) or private prescribing services. A prescriber may start you on a lower dose and titrate gradually, and maximum dose may not be reached or necessary depending on your response and tolerability.
- Both work best alongside a reduced-calorie diet and increased physical activity
- Individual weight loss varies significantly between people
- Track your progress using our free progress tracker to monitor results over time
- 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 is the maximum dose of Mounjaro for weight loss in the UK?
The maximum dose of Mounjaro (tirzepatide) is 15 mg once weekly. Escalation happens over 20 weeks, increasing by 2.5 mg every 4 weeks. Not all patients require or tolerate the maximum dose — your prescriber will adjust based on your individual response and any side effects.
What is the maximum dose of Wegovy?
The maximum dose of Wegovy (semaglutide) is 2.4 mg once weekly. The dose escalation schedule takes 16 weeks, starting at 0.25 mg and increasing every 4 weeks. Like Mounjaro, the maximum dose may not be necessary or suitable for everyone.
Which medication causes more weight loss — Mounjaro or Wegovy?
Clinical trials show Mounjaro achieved average weight loss of 15–21% at maximum dose, while Wegovy achieved approximately 14.9%. However, these are trial averages — individual results vary significantly. A prescriber will assess which is suitable for you based on your personal health circumstances.
Can I switch from Wegovy to Mounjaro or vice versa?
Switching between medications must be managed by your prescriber. Approximate dose equivalences exist (e.g., Wegovy 2.4 mg is roughly equivalent to Mounjaro 15 mg), but there is no official conversion chart. Your prescriber will guide the process, including any washout period needed.
How do I know which medication I'm eligible for in the UK?
UK prescribing eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions. Use our free BMI calculator to check your BMI, then consult your GP or a licensed prescriber for a clinical assessment. Both Mounjaro and Wegovy require a prescription and suitability assessment.
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.