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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How to Work Out Your M2 — UK Health Information
M2 (also called "body mass index multiplied by body fat percentage") is an advanced body composition metric used in UK health assessment to provide a more detailed picture of your health status than BMI alone. Unlike standard BMI, which doesn't distinguish between muscle and fat, M2 helps identify whether excess weight comes from muscle or adipose tissue. This guide explains what M2 means, how to calculate it, and why it matters for your health according to NHS guidance. You can use our free BMI calculator and weight converter to support your personal health tracking.
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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 M2 Works and Why It Matters
M2 combines two key measurements:
- Your BMI (body mass index)
- Your estimated or measured body fat percentage
The formula is: BMI × (body fat % ÷ 100) = M2. This gives a more nuanced view than BMI alone because it accounts for body composition. Two people with the same BMI can have very different M2 values if one has high muscle mass and the other has high body fat. M2 is particularly useful for athletes or very muscular individuals, where standard BMI may overestimate health risk. NHS guidance recognises that waist circumference and body composition matter alongside BMI for accurate health assessment. M2 helps bridge this gap by incorporating body fat data into your overall health profile.
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
M2 Eligibility and Next Steps for UK Adults
To calculate your M2, you'll need your height, weight, and body fat percentage. Body fat can be measured via DEXA scan, bioelectrical impedance, or estimated using online calculators (though measured data is more accurate). Start with our free weight converter to confirm your measurements in kg and cm. Most UK GPs do not routinely measure M2, but specialist weight management services and private health clinics often do. If you're interested in detailed body composition assessment, ask your GP about referral to NHS tier 3 weight management services, which can provide professional body composition analysis. This information helps create personalised healthy weight UK plans tailored to your individual health goals.
- 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 M2 and how is it different from BMI?
M2 combines BMI with body fat percentage to give a clearer picture of body composition than BMI alone. While BMI treats all weight equally (not distinguishing muscle from fat), M2 accounts for whether excess weight is muscle or adipose tissue. This makes M2 especially useful for athletes or very muscular people, where standard BMI can be misleading. NHS health advice recognises that body composition matters for accurate health assessment.
How do I calculate my M2?
Use the formula: BMI × (body fat % ÷ 100) = M2. First, calculate your BMI using our free BMI calculator. Then obtain your body fat percentage via DEXA scan, bioelectrical impedance, or online estimation. Multiply your BMI by your body fat percentage divided by 100. MyWeightCheck's weight converter can help you confirm your height and weight in the correct units.
Why should I care about M2 if I already know my BMI?
BMI doesn't distinguish between muscle and fat, so it can overestimate health risk in muscular people or underestimate it in sedentary people with high body fat. M2 provides a more complete picture. Healthy weight UK assessment ideally includes multiple measures: BMI, waist circumference, and body composition. This helps your GP or healthcare professional give more personalised weight management advice.
How can I access M2 body composition testing in the UK?
Your GP can refer you to NHS tier 3 weight management services, which often include body composition assessment. Private health clinics and sports medicine providers also offer DEXA scans and bioelectrical impedance testing. Some fitness centres provide basic body fat estimation. For weight management guidance, start with NHS health advice or our free BMI calculator and weight converter to establish your baseline health metrics.
Is M2 recognised by the NHS?
While M2 is not a standard NHS metric, the NHS strongly emphasises that body composition matters alongside BMI. NHS guidance recommends measuring waist circumference and considering overall health markers rather than BMI alone. Your GP can discuss whether specialist body composition assessment would be helpful for your personal health plan.
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.