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 BMI Is Healthy?
A healthy BMI (Body Mass Index) falls between 18.5 and 24.9 according to NHS guidelines. However, BMI is just one health indicator — it doesn't account for muscle mass, bone density, or where fat is stored. Your age, ethnicity, and overall fitness level all matter too. This guide explains what a healthy BMI actually means, how to interpret your personal BMI range, and why it's worth using other health measures alongside it. Use our free BMI calculator above to check your personal BMI instantly.
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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 Healthy Ranges
The NHS BMI categories are standardised across the UK and apply to adults aged 18 and over:
- Underweight: BMI below 18.5
- Healthy weight: BMI 18.5 to 24.9
- Overweight: BMI 25.0 to 29.9
- Obese (Class I): BMI 30.0 to 34.9
- Obese (Class II): BMI 35.0 to 39.9
- Severely obese (Class III): BMI 40.0 and above
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds due to higher health risk at the same BMI level. For these groups, a healthy BMI is 18.5 to 22.9, and overweight starts at 23.0. These adjusted BMI categories UK reflect the latest clinical evidence about cardiovascular and metabolic risk in different populations.
To calculate your BMI range uk at your height, the healthy weight range is roughly 18.5 to 24.9 times your height in metres squared. Try our bmi calculator on this page to find your exact range instantly.
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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.
Why BMI Alone Isn't the Whole Picture
The bmi formula (weight in kg ÷ height in metres²) is useful for screening but has significant bmi limitations. It cannot distinguish between muscle and fat — an athlete with high muscle mass may have a high BMI but low body fat percentage. Overweight bmi threshold definitions also don't account for age-related muscle loss, bone structure, or where your weight sits on your body.
For a more complete health picture, also consider: waist circumference (men over 102cm, women over 88cm indicate increased health risk), waist-to-height ratio (healthy is below 0.5), and body fat percentage. Your GP can discuss your personal health using BMI alongside these other measures. Use our weight converter to check your weight in different units, and our 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.
Is a BMI of 25 considered healthy?
A BMI of 25 falls in the "overweight" category according to NHS guidelines, not the healthy range. Healthy BMI is 18.5 to 24.9. However, BMI is just a screening tool — your overall health depends on fitness, diet, genetics, and other factors. Speak to your GP about what's right for you personally.
What is the healthiest BMI for my age?
The NHS BMI categories apply to all adults aged 18 and over regardless of age. However, older adults naturally lose muscle mass over time, which can affect how BMI relates to actual body composition. Your GP can give you personalised guidance about a healthy weight range for your age and health status.
Why does my ethnicity matter for BMI?
Research shows that South Asian, Chinese, Black African, and Black Caribbean populations have higher risk of type 2 diabetes and heart disease at lower BMI levels compared to white European populations. The NHS recommends lower BMI thresholds for these groups — healthy BMI starts at 18.5 to 22.9 rather than 18.5 to 24.9.
Can I have a healthy BMI but be unhealthy?
Yes. BMI doesn't measure fitness, muscle mass, cholesterol, blood pressure, or mental health. Someone with a healthy BMI could still have high blood pressure or poor cardiovascular fitness, while someone slightly above the healthy range might be very fit. Use BMI as one indicator, not the whole picture.
How do I calculate a healthy weight range for my height?
Multiply your height in metres by itself, then multiply by 18.5 (lower healthy bound) and by 24.9 (upper healthy bound). For example, at 1.70m tall: 18.5 × (1.70)² = 53.4 kg; 24.9 × (1.70)² = 71.9 kg. So healthy weight is roughly 53.4 to 71.9 kg. Use our BMI calculator above for gradual improvement.
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.