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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Weight and BMI Chart — NHS Health Guidance
Understanding your weight in relation to your height is one of the most important health checks you can do. This guide explains the NHS BMI categories, how to use a weight and BMI chart to assess your health, and what the different ranges mean for you. We'll cover the official NHS guidance, BMI formula, and when you should speak to your GP about your weight. Use our free BMI calculator above to check your personal BMI instantly, and see where you fall on the NHS chart.
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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 Healthy Weight Ranges
The NHS BMI chart divides adults into four main categories based on their weight and height. These are the official UK health thresholds:
- Underweight: BMI below 18.5 — may indicate insufficient weight or underlying health concerns
- Healthy weight: BMI 18.5 to 24.9 — the target range recommended by the NHS and NICE for optimal health
- Overweight: BMI 25.0 to 29.9 — increased risk of weight-related health conditions
- Obese: BMI 30.0 and above, further divided into Class I (30–34.9), Class II (35–39.9), and Class III (40+)
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds: healthy weight is BMI 18.5–22.9, and overweight begins at 23.0. This reflects higher health risks at lower BMI in these populations. The healthy BMI range formula is simple: 18.5 × height(m)² to 24.9 × height(m)² gives you your personal healthy weight range in kilograms.
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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 Support and When to Seek Help
The NHS weight management pathway has four tiers of support. Tier 1 includes self-help tools and digital programmes you can access yourself. Tier 2 offers primary care-based behaviour change support through your GP. Tier 3 is specialist multidisciplinary weight management services — this is where prescription weight loss medications like Mounjaro and Wegovy are typically prescribed following clinical assessment. Tier 4 covers bariatric surgery for severe obesity with significant health complications.
Speak to your GP if: your BMI is 25 or above with weight-related health conditions (high blood pressure, type 2 diabetes, sleep apnoea); your BMI is 30 or above; or you're struggling with weight management despite lifestyle changes. Your GP can assess your individual situation and refer you to the appropriate support level. Track your progress with our free 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 BMI should I aim for according to NHS guidance?
The NHS recommends a healthy BMI between 18.5 and 24.9 for most UK adults. If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy range is 18.5–22.9. Your GP can discuss your individual target based on your health conditions and circumstances.
How accurate is the BMI chart for assessing health?
BMI is a useful screening tool but has important limitations. It doesn't distinguish between muscle and fat — athletes may have a high BMI but low body fat. It also doesn't account for where fat is stored or age-related muscle loss. The NHS recommends using BMI alongside waist circumference and other health markers.
What is the BMI formula and can I calculate it myself?
The BMI formula is weight (kg) divided by height (metres) squared. For example, a person weighing 70kg who is 1.75m tall: 70 ÷ (1.75)² = BMI of 22.9. Use our free BMI calculator above to calculate your BMI instantly without doing the maths yourself.
At what BMI should I speak to my GP about weight management?
The NHS recommends speaking to your GP if your BMI is 25 or above with weight-related health conditions, or 30 or above regardless of other conditions. Your GP can assess whether weight management support — including lifestyle changes, behaviour programmes, or prescription medication — is appropriate for you.
Does the weight and BMI chart differ between men and women?
No — the NHS BMI categories are the same for both men and women. However, healthy body fat percentages do differ by sex. BMI alone doesn't account for body composition differences. Your GP can provide personalised guidance based on your sex, age, ethnicity, and health status.
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.