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 Healthy BMI Range?
A healthy BMI range according to NHS guidelines is between 18.5 and 24.9. Your BMI (body mass index) is calculated using your height and weight, and it's used as a screening tool to assess whether you're at a healthy weight. However, the healthy BMI range can vary depending on your ethnicity and age. Use our free BMI calculator above to check where you fall, and this guide explains what your result means for your 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 Healthy Weight Ranges
The NHS BMI formula divides your weight in kilograms by your height in metres squared. Here are the official BMI categories UK adults fall into:
- Below 18.5: Underweight
- 18.5 to 24.9: Healthy weight (the healthy BMI range)
- 25.0 to 29.9: Overweight
- 30.0 to 34.9: Obese (Class I)
- 35.0 to 39.9: Obese (Class II)
- 40.0 and above: Severely obese (Class III)
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the overweight BMI threshold is lower. A healthy BMI for these groups is 18.5 to 22.9, and overweight begins at 23.0. This reflects research showing these populations face higher health risks at lower BMI levels. Calculate your personal BMI instantly using the BMI calculator on this page to find out which category you fall into.
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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.
Understanding BMI Limitations and Other Health Measures
While BMI is a useful screening tool, it has important BMI limitations. BMI doesn't distinguish between muscle and fat — athletes may have a high BMI but very low body fat. It also doesn't account for where fat is stored, which matters for health: fat around your middle poses greater cardiovascular risk than fat elsewhere. Age, bone density, and pregnancy also affect how accurate BMI is for individuals.
The NHS recommends also measuring waist circumference as part of a health assessment. For men, a waist over 94cm increases health risk; over 102cm is high risk. For women, over 80cm is increased risk; over 88cm is high risk. Your GP can discuss your personal healthy weight range, factoring in your overall health, fitness level, and family history.
- 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 for UK adults?
The healthy BMI range for UK adults is 18.5 to 24.9 according to NHS guidelines. For adults 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 you personally.
How do I calculate my BMI?
BMI is calculated by dividing your weight in kilograms by your height in metres squared (weight ÷ height²). Use our free BMI calculator above to calculate instantly, or convert your weight using our weight converter first if you use stone and pounds.
Is BMI accurate for everyone?
No. BMI doesn't account for muscle mass, bone density, age, or where fat is stored. Athletes may have high BMI but low body fat. Your GP should assess your overall health, not just BMI, when discussing your weight.
What weight should I aim for?
Your healthy weight range depends on your height, age, ethnicity, and overall health. Use the BMI calculator to find the weight range that gives you a BMI of 18.5 to 24.9. Your GP can provide personalised guidance based on your individual circumstances.
Should I be concerned if my BMI is over 25?
A BMI over 25 falls in the overweight category, but this doesn't mean you're automatically unhealthy. Your GP considers other factors like waist measurement, fitness level, blood pressure, and family history. Even modest weight loss of 5–10% can improve health outcomes.
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.