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
What Is a Normal BMI Index Range?
A normal or healthy body mass index (BMI) for UK adults falls between 18.5 and 24.9, according to NHS guidelines. This range is based on scientific research linking BMI to health risks, and it applies to most adults aged 18 and over. However, BMI is just one health screening tool — your individual circumstances, ethnicity, and overall health matter too. Understanding your BMI range is a helpful starting point for assessing your weight health, but it should always be considered alongside other factors like waist measurement and overall fitness.
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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.
Understanding the NHS BMI Categories and Ranges
The body mass index is calculated by dividing your weight in kilograms by your height in metres squared (kg ÷ m²). The NHS uses this formula to categorise adults into five main BMI categories UK health professionals rely on:
- Underweight: BMI below 18.5
- Normal/healthy weight: BMI 18.5–24.9 (this is the target range)
- Overweight: BMI 25.0–29.9
- Obese (Class I): BMI 30.0–34.9
- Obese (Class II): BMI 35.0–39.9
- Severely obese (Class III): BMI 40.0 and above
For example, an adult 1.73 metres tall (5ft 8in) with a normal BMI would weigh between approximately 55 kg and 74 kg (8st 10lbs to 11st 10lbs). Use our free BMI calculator above to check your personal BMI instantly and see which category you fall into. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI range UK thresholds apply — the healthy range starts at 18.5 but extends only to 22.9, reflecting higher health risks at lower weights in these populations.
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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 a healthy BMI is useful, it has important limitations. BMI does not distinguish between muscle and fat — athletes may have a high BMI but low body fat. It also ignores where fat is stored (belly fat carries greater health risk than fat elsewhere) and does not account for age-related muscle loss. Alongside BMI, the NHS BMI guidelines recommend measuring your waist circumference: men should aim for under 94 cm (37in), and women under 80 cm (31.5in) for healthy risk levels. Your GP can provide personalised advice about what your overweight BMI threshold or healthy BMI means for your specific health. Converting your weight using our free weight converter helps you track changes across kg, stone, and lbs.
- 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 considered a normal BMI for adults in the UK?
According to NHS guidelines, a normal or healthy BMI for UK adults is between 18.5 and 24.9. This range applies to most adults aged 18 and over. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy range is 18.5 to 22.9 due to increased health risks at higher weights in these groups.
How is BMI calculated?
The BMI formula divides your weight in kilograms by your height in metres squared (kg ÷ m²). For example, a person weighing 70 kg and 1.75 metres tall would have a BMI of 70 ÷ (1.75 × 1.75) = 22.9, which falls in the healthy range. Our BMI calculator performs this instantly.
What does BMI not tell you about health?
BMI does not distinguish between muscle and fat, so athletes may have a high BMI despite being fit. It also ignores where fat is stored (belly fat is riskier than other fat) and does not account for age, bone density, or medical conditions. Waist circumference and overall fitness are equally important health measures.
Are BMI ranges the same for everyone?
No. The NHS recommends lower BMI thresholds for people of South Asian, Chinese, Black African, and Black Caribbean heritage because these groups face higher risks of type 2 diabetes and heart disease at lower BMI levels. Your GP can advise on what a healthy weight means for you specifically.
What should I do if my BMI is outside the normal range?
If your BMI is below 18.5 or above 25, speak to your GP for personalised advice. Small lifestyle changes, including diet and physical activity adjustments, can help. Your GP can discuss whether additional support or monitoring is needed based on your individual health circumstances.
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.