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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NHS BMI Table and Health Categories
The NHS BMI table is the standard tool used across the UK to assess whether an adult's weight falls within a healthy range. Your BMI (body mass index) is calculated from your height and weight, and the NHS uses specific categories to help you understand your health risk. This guide explains the official NHS BMI ranges, how to interpret your results, and what the NHS recommends if your BMI falls outside the healthy zone. Use our free BMI calculator above to find your personal BMI instantly and see where you sit on the official NHS scale.
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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 What They Mean
The NHS BMI categories divide adults into five main groups based on health risk. These are the official UK health thresholds endorsed by NICE (National Institute for Health and Care Excellence) and used by GPs across the country:
- Underweight: BMI below 18.5 — may indicate nutritional deficiency or health concerns
- Healthy weight: BMI 18.5 to 24.9 — the target range for most adults
- Overweight: BMI 25.0 to 29.9 — increased health risks begin to appear
- Obese (Class I): BMI 30.0 to 34.9 — elevated risk of weight-related conditions
- Obese (Class II): BMI 35.0 to 39.9 — higher health risks including type 2 diabetes
- Severely obese (Class III): BMI 40.0 and above — significant health risks requiring medical attention
It's important to understand that BMI limitations exist — BMI does not distinguish between muscle and fat, so athletes with high muscle mass may have a high BMI despite low body fat. Your GP can provide personalised interpretation of your individual result.
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.
NHS Weight Management Support and Next Steps
If your BMI falls outside the healthy range, the NHS offers a structured weight management pathway tailored to your needs. At tier 1, you can access free digital tools and community programmes. Tier 2 involves your GP practice offering behaviour change support and structured weight loss programmes. For those with a BMI of 30 or above (or 27–29.9 with weight-related health conditions), tier 3 specialist services are available, where prescription weight loss medications may be considered alongside lifestyle changes.
The NHS also recommends measuring your waist circumference alongside BMI: for men, over 94cm indicates increased risk; for women, over 80cm indicates increased risk. These measurements together give a clearer picture of health risk than BMI alone. Chat with your GP about the right next step for you.
- 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 healthy BMI range according to the NHS?
The NHS defines a healthy BMI as 18.5 to 24.9 for most adults. However, for people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds of 18.5 to 22.9 because these groups face higher health risks at the same BMI levels.
How do I calculate my BMI using the NHS formula?
The BMI formula is your weight in kilograms divided by your height in metres squared. For example, if you weigh 70kg and are 1.75m tall, your BMI is 70 ÷ (1.75 × 1.75) = 22.9. Use our free BMI calculator on this page to work this out instantly without a UK pharmacy calculation.
What should I do if my BMI is over 30?
If your BMI is 30 or above, contact your GP to discuss weight management support. The NHS offers a stepped care pathway: you can start with tier 1 digital tools and community programmes, or your GP can refer you to specialist services. Weight loss of even 5–10% can bring meaningful health benefits.
Does the NHS BMI table apply to children?
No — children and teenagers use different BMI calculations based on age and sex-specific growth charts (UK90 reference). The adult NHS BMI categories do not apply to children. Always speak to your GP or health visitor for children's weight guidance.
Are there any limitations to using the NHS BMI table?
Yes — BMI does not account for muscle mass versus fat, where fat is stored (waist measurement matters), or individual variation. The NHS recommends using BMI alongside waist circumference measurement and discussing your personal health context with your GP for a complete picture.
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.