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
UK BMI Chart — NHS Categories and Health Guidance
A UK BMI chart helps you understand whether your weight falls into a healthy range according to NHS guidelines. BMI (body mass index) is calculated using your height and weight, and the NHS uses standardised BMI categories to assess health risk. This guide explains the NHS BMI categories, how to interpret your results, and when to seek support from your GP. Use our free BMI calculator above to find your personal BMI instantly.
10,000+ calculations today · NHS-aligned thresholds · 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/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 What They Mean
The NHS uses five main BMI categories to classify adult weight status. These are based on research showing health risk at different BMI ranges:
- Underweight (BMI below 18.5): May indicate nutritional deficiency or other health concerns — speak to your GP if you're consistently underweight
- Healthy weight (BMI 18.5–24.9): Associated with the lowest health risk — the target range for most UK adults
- Overweight (BMI 25.0–29.9): Increased risk of weight-related health conditions including type 2 diabetes and high blood pressure
- Obese Class I (BMI 30.0–34.9): Significantly increased health risk — NHS recommends weight management support
- Obese Class II (BMI 35.0–39.9): High health risk — medical intervention may be recommended
- Severely obese (BMI 40.0+): Very high health risk — specialist NHS support typically available
These BMI ranges UK apply to adults aged 18 and over. Children use different age- and sex-specific charts.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
NHS Weight Management and When to Seek Help
The NHS recognises that weight management is important for health and offers support through a four-tier pathway. Your GP can assess your individual situation and refer you to appropriate services. Even modest weight loss — around 5–10% of your current weight — can significantly improve blood sugar control, blood pressure, and reduce strain on joints. If your BMI falls into the overweight or obese categories, or if you have weight-related health concerns, speak to your GP about what support is available in your area. Our free weight converter can help you understand your weight in different units whilst you work with your healthcare team.
- 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's the difference between the NHS BMI chart and other BMI calculators?
The NHS BMI chart is based on research specific to UK populations and aligned with NICE (National Institute for Health and Care Excellence) guidance. It uses the same formula as international charts but the UK health thresholds and categories reflect NHS clinical recommendations. The healthy BMI range is 18.5–24.9 for most adults, though lower thresholds apply to some ethnic groups.
Does the NHS BMI chart account for muscle mass?
No — this is a key limitation of BMI. The formula doesn't distinguish between muscle and fat. Athletes or very muscular individuals may have a high BMI despite low body fat. Your GP can assess body composition more comprehensively if this is relevant to you.
Are the NHS BMI categories the same for everyone?
No. The NHS recommends lower BMI thresholds for adults of South Asian, Chinese, Black African, and Black Caribbean heritage because these groups face higher health risks at the same BMI. Your GP can discuss thresholds relevant to your individual background and health.
What does the NHS recommend if my BMI is in the overweight range?
The NHS recommends lifestyle changes including a balanced diet and increased physical activity. Your GP can discuss weight management options, including referral to structured weight loss programmes, dietary support, or — if appropriate — prescription weight loss medication through specialist services.
Can I use the BMI formula myself instead of a chart?
Yes — the formula is BMI = weight (kg) ÷ height (metres)². However, our free BMI calculator above does this automatically and instantly shows you where you fall on the NHS chart, which is quicker and more reliable than a UK pharmacy calculation.
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.