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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BMI Indicator Chart: NHS Categories and What Your Score Means
A BMI indicator chart helps you understand where your weight falls according to NHS guidelines. Your BMI (Body Mass Index) is calculated from your height and weight, and the NHS uses standardised categories to indicate whether you're at a healthy weight or if excess weight might be affecting your health. This guide explains the NHS BMI ranges, how to interpret your score, and what NHS support is available if needed.
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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.
NHS BMI Categories and NICE Guidance
The NHS BMI formula divides weight (in kilograms) by height (in metres) squared. The resulting score places you in one of five categories according to NHS guidance:
- Underweight: BMI below 18.5 — may indicate insufficient weight for optimal health
- Healthy weight: BMI 18.5–24.9 — the target range recommended by NHS and NICE
- Overweight: BMI 25.0–29.9 — increased health risks; lifestyle changes recommended
- Obese (Class I): BMI 30.0–34.9 — significant health risks; GP support advised
- Obese (Class II): BMI 35.0–39.9 — high health risks; NHS intervention recommended
- Severely obese (Class III): BMI 40.0 and above — very high health risks; urgent GP assessment recommended
The healthy BMI range of 18.5–24.9 is where the NHS focuses prevention efforts. However, for adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds — a healthy BMI starts at 18.5 but overweight begins at BMI 23.0, reflecting higher cardiovascular risk in these populations at lower BMI levels.
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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.
NHS Weight Management Pathway and When to Seek Help
The NHS offers a structured approach to weight management across four tiers. Tier 1 involves self-help tools and community programmes — MyWeightCheck's free BMI calculator can support this stage by helping you track where you stand. Tier 2 brings primary care involvement through your GP, who can assess your individual health risks and recommend the NHS Weight Loss Plan or behaviour change support. If your BMI exceeds 30, or you have a BMI of 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure, ask your GP about referral to Tier 3 specialist weight management services. Tier 4 covers bariatric surgery for severe obesity. Your GP can advise which tier is appropriate for your circumstances and provide ongoing support throughout your weight management journey.
- 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 a healthy BMI according to NHS guidelines?
The NHS defines a healthy BMI as 18.5 to 24.9 for most UK adults. For adults of South Asian, Chinese, Black African, or Black Caribbean backgrounds, the NHS recommends a healthy range of 18.5 to 22.9 due to higher health risks at elevated BMI in these populations. Use our free BMI calculator to check your personal score.
What does the BMI indicator chart tell me if I'm overweight but not yet obese?
A BMI between 25.0 and 29.9 indicates overweight status. The NHS recommends lifestyle changes — increased physical activity, reduced calorie intake, and behaviour support — to prevent progression to obesity and reduce cardiovascular disease risk. Your GP can provide personalised guidance.
Does the BMI chart apply to children and teenagers?
No. Children and teenagers use different BMI centile charts based on age and sex — adult BMI categories do not apply. If you're concerned about a young person's weight, consult your GP or use the NHS Healthy Weight Calculator for children, which provides age-appropriate guidance.
Why does the NHS BMI chart have lower thresholds for some ethnic groups?
Research shows that South Asian, Chinese, Black African, and Black Caribbean adults face higher risks of type 2 diabetes, heart disease, and stroke at lower BMI levels than other populations. The NHS adjusted thresholds (healthy weight up to BMI 22.9 instead of 24.9) reflect this evidence and help identify risk earlier in these communities.
What should I do if my BMI is above the healthy range?
Start by speaking to your GP, who can assess your individual health, discuss contributing factors (genetics, medications, health conditions), and recommend appropriate support. This might include tier 2 or tier 3 NHS weight management services, behaviour change programmes, or referral to a dietitian. The NHS Weight Loss Plan is also freely available online as a self-help starting point.
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.