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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Body Mass Index (BMI) Chart for Adults — NHS Guidelines
Your Body Mass Index (BMI) is a useful health screening tool that helps you and your GP understand whether your weight is in a healthy range for your height. The NHS uses specific BMI categories to assess health risk in UK adults. This guide explains the BMI formula, NHS thresholds, and what your BMI means for your health. Use our free BMI calculator above to find your personal BMI instantly, and discover whether it falls within the NHS healthy weight range.
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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.
NHS BMI Categories and Healthy Weight Ranges
The NHS recommends a healthy BMI of 18.5 to 24.9 for most UK adults. Your BMI is calculated by dividing your weight in kilograms by your height in metres squared (or using the formula: weight in pounds × 703 ÷ height in inches squared). The BMI range chart below shows NHS standard categories:
- Below 18.5: Underweight — may indicate nutritional risk
- 18.5–24.9: Healthy weight — lowest health risk range
- 25.0–29.9: Overweight — increased health risks begin
- 30.0–34.9: Obese (Class I) — significantly elevated risk
- 35.0–39.9: Obese (Class II) — high risk
- 40.0+: Severely obese (Class III) — very high risk
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds: healthy weight is 18.5–22.9, and overweight begins at 23.0. This reflects higher cardiovascular and diabetes risk in these groups at lower BMI levels.
Clinically BackedWeight Loss
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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.
Understanding BMI Limitations and NHS Weight Management Support
BMI is a useful screening tool, but it has important limitations. BMI does not distinguish between muscle and fat — athletes may have a high BMI but low body fat percentage. It also does not account for where fat is stored; waist measurement matters too. The NHS recommends measuring waist circumference alongside BMI: over 94cm (37in) for men or 80cm (31.5in) for women indicates increased health risk.
If your BMI falls outside the healthy range, the NHS offers a structured weight management pathway. Your GP can refer you to Tier 1 support (digital tools and community programmes), Tier 2 services (primary care behaviour change programmes), or Tier 3 specialist weight management services where prescription medications and intensive support are available. Use our free weight converter to check your weight in different units, and our progress tracker to monitor changes 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 BMI formula and how do I calculate it?
BMI = weight (kg) ÷ height (m)². For example, if you weigh 70kg and are 1.75m tall, your BMI is 70 ÷ (1.75)² = 22.9 (healthy weight). Use our free BMI calculator above for gradual improvement without a UK pharmacy calculation.
What does "healthy BMI" mean according to the NHS?
The NHS defines healthy BMI as 18.5–24.9 for most UK adults. For South Asian, Chinese, Black African, and Black Caribbean adults, the healthy range is 18.5–22.9 due to higher health risks at higher BMI levels in these populations.
Is BMI accurate for everyone, including athletes and older adults?
BMI has limitations. It doesn't distinguish muscle from fat, so athletic individuals may have high BMI but low body fat. In older adults, BMI may not account for age-related muscle loss. Your GP can assess your individual health context beyond BMI alone.
When should I contact my GP about my BMI or weight?
Contact your GP if your BMI is consistently below 18.5 or above 25, especially if you have weight-related symptoms like joint pain, breathlessness, or family history of diabetes. Your GP can offer personalised advice and referral to NHS weight management support if appropriate.
What is the difference between overweight and obese according to NHS guidelines?
The NHS defines overweight as BMI 25.0–29.9 and obese as BMI 30.0 and above. These categories reflect increasing health risks. Obese is further divided into Class I (30–34.9), Class II (35–39.9), and Class III/severely obese (40+). Each carries progressively higher disease risk.
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.