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
Free tracker included with every download this week
BMI Normative Data — What the Numbers Mean
BMI normative data refers to the average BMI ranges across populations and the standard categories used by the NHS to assess weight and health risk. In the UK, normative BMI data helps healthcare professionals and individuals understand whether a weight sits within a healthy range, and what health risks may be associated with different BMI levels. This guide explains the key benchmarks, how they're calculated, and why context matters when interpreting your own BMI.
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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.
UK BMI Categories and Average Population Data
The NHS BMI formula divides weight in kilograms by height in metres squared (BMI = kg ÷ m²). The resulting number falls into standardised BMI categories that apply to adults aged 18 and over:
- Underweight: below 18.5
- Healthy weight: 18.5–24.9
- Overweight: 25.0–29.9
- Obese (Class I): 30.0–34.9
- Obese (Class II): 35.0–39.9
- Severely obese (Class III): 40.0 and above
According to recent UK data, the average adult BMI is approximately 27.6, placing the population in the overweight category. However, BMI range UK norms vary by age, sex, and ethnicity. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds — healthy weight begins at BMI 18.5 but overweight starts at 23.0, reflecting higher cardiovascular and metabolic risk at lower BMI levels in these groups.
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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.
BMI Limitations and Complementary Measures
While BMI is a useful screening tool, BMI limitations mean it should never be the only measure of health. BMI does not distinguish between muscle and fat — athletes and people with high muscle mass may have a high BMI despite low body fat. It also ignores where fat is stored; central obesity (fat around the abdomen) carries higher health risk than fat distributed elsewhere. Age, pregnancy, and ethnicity also affect BMI accuracy.
The NHS recommends using BMI alongside waist circumference measurement for a fuller picture. A healthy BMI combined with a waist circumference below 80cm (women) or 94cm (men) indicates lower health risk. Use our free BMI calculator above to check your personal BMI, then discuss the results with your GP for personalised interpretation.
- 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 average BMI in the UK?
The average adult BMI in the UK is approximately 27.6, which falls in the overweight category according to NHS guidelines. However, this varies significantly by age, sex, and ethnicity. Around 63% of UK adults are overweight or obese (BMI 25 or above), while 28% meet the criteria for obesity (BMI 30 or above).
Why are BMI thresholds different for South Asian and Black African populations?
Research shows that people of South Asian, Chinese, Black African, and Black Caribbean heritage face higher health risks from type 2 diabetes and cardiovascular disease at lower BMI levels compared to white European populations. The NHS therefore recommends lower BMI thresholds for these groups — overweight begins at BMI 23 rather than 25, reflecting their genuine health risk profile.
What does a healthy BMI range actually mean for me?
A healthy BMI (18.5–24.9 for most adults) indicates lower risk of weight-related health problems like type 2 diabetes and heart disease. However, healthy BMI is just one factor in overall health. Your actual health depends on fitness, diet, stress levels, sleep, medical history, and genetics. Your GP can discuss what a healthy BMI means specifically for you.
Is BMI still accurate if I have high muscle mass?
No — BMI cannot distinguish between muscle and fat. Athletes and very fit individuals may have a high BMI despite low body fat percentage. If you have significant muscle mass, discuss your BMI with your GP. They may recommend waist circumference or body composition analysis for a clearer picture of your actual health risk.
How do I calculate my own BMI?
Use the formula: weight (kg) ÷ height (m)². For example, someone weighing 70kg and 1.73m tall would have a BMI of 23.4. Alternatively, use our free BMI calculator on this page — it handles the maths instantly and tells you which NHS category your BMI falls into, plus your healthy weight range.
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.