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 Index Table: UK Categories and Ranges Explained
A BMI index table shows you where your weight sits within standard health categories according to NHS guidelines. Your body mass index is calculated by dividing your weight in kilograms by your height in metres squared — a simple screening tool that helps identify whether you're in a healthy weight range. This guide explains the BMI ranges used in the UK, how to interpret your personal BMI, and why medical professionals use this metric as part of assessing overall health.
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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 index table divides adults into five main categories based on their body mass index score:
- Underweight: BMI below 18.5
- Healthy weight: BMI 18.5–24.9 (the target range)
- Overweight: BMI 25.0–29.9
- Obese (Class I): BMI 30.0–34.9
- Severely obese (Class II & III): BMI 35.0 and above
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds due to increased health risks at lower BMI levels. For these groups, a healthy BMI range is 18.5–22.9, and overweight begins at BMI 23.0. You can calculate your personal BMI instantly using our free BMI calculator above to see exactly where you fall on this index table.
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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.
BMI Limitations and Complementary Health Measures
While the BMI formula is a useful screening tool, it has important limitations. BMI does not distinguish between muscle and fat — muscular individuals or athletes may have a high BMI despite low body fat. BMI also ignores where fat is stored; waist circumference is equally important for assessing health risk. For men, increased risk begins above 94cm (37 inches) of waist circumference; for women, above 80cm (31.5 inches). Your GP can assess your BMI alongside other factors like blood pressure, cholesterol, and family history to give you a complete health picture. Use our free weight converter to check your weight in different units alongside your BMI.
- 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 range is considered healthy in the UK?
According to NHS guidelines, a healthy BMI for most UK adults is 18.5 to 24.9. This range is associated with the lowest health risks. However, for people of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy range is lower: 18.5 to 22.9. Your GP can advise on what's healthy for your individual circumstances.
How is BMI calculated?
BMI is calculated using the formula: weight (kg) divided by height (metres) squared. For example, someone weighing 70kg and 1.75m tall would have a BMI of 70 ÷ (1.75 × 1.75) = 22.9. Our free BMI calculator on this page does this instantly for you.
Is BMI accurate for muscular people?
No — BMI doesn't distinguish between muscle and fat. Muscular or athletic individuals may have a higher BMI despite low body fat percentage. This is why your GP considers other measures like waist circumference and overall health markers, not just BMI alone.
What does it mean if my BMI is in the overweight category?
A BMI of 25.0–29.9 falls in the overweight range according to NHS guidelines. This doesn't mean you're ill, but it does suggest a modest health benefit from gradual weight loss through diet and activity. Your GP can discuss whether this is appropriate for you personally.
Why are BMI thresholds lower for some ethnic groups?
Research shows that people of South Asian, Chinese, Black African, and Black Caribbean heritage develop weight-related health conditions like type 2 diabetes at lower BMI levels than other groups. The NHS therefore recommends lower BMI thresholds for these populations to identify increased risk earlier.
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.