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 Good BMI Range?
A good BMI range according to NHS guidelines is between 18.5 and 24.9, which is classified as a healthy weight. Your BMI (body mass index) is calculated using your height and weight, and it's a useful screening tool for assessing whether you're in a healthy weight range for your age and sex. However, BMI alone doesn't tell the whole story about your health — other factors like muscle mass, where fat is stored, and overall fitness also matter. Use our free BMI calculator above to check your personal BMI instantly and see where you fall on the 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 Healthy Weight Ranges
The NHS BMI categories divide adults into five groups based on their body mass index. A good BMI range starts at 18.5 and tops out at 24.9, representing a healthy weight where health risks from excess weight are lowest.
- 18.5 – 24.9: Healthy weight (good BMI range)
- 25.0 – 29.9: Overweight
- 30.0 – 34.9: Obese (Class I)
- 35.0 – 39.9: Obese (Class II)
- 40.0+: Severely obese (Class III)
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds apply — a healthy BMI range is 18.5 to 22.9, reflecting higher health risks at lower weight levels in these populations. Use the BMI formula (weight in kg ÷ height in m²) to calculate your own BMI, or use our free BMI calculator for gradual improvement.
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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 Other Health Measures
A good BMI range is a helpful guide, but BMI limitations mean it's not the complete picture. BMI doesn't distinguish between muscle and fat — athletes may have a high BMI but low body fat. It also ignores where fat is stored; excess belly fat carries greater health risk than fat stored elsewhere. Your waist circumference matters too: men should aim for under 94cm (37 inches), women under 80cm (31.5 inches). Consider your family history, fitness level, blood pressure, and cholesterol alongside your BMI. Your GP can assess your overall health risk and recommend next steps if needed.
- 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 good BMI range according to NHS guidelines?
The good BMI range is 18.5 to 24.9, classified as healthy weight. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, a healthy BMI range is 18.5 to 22.9 due to higher health risks at lower BMI levels in these populations.
How do I calculate my BMI to see if I'm in the good range?
Divide your weight in kilograms by your height in metres squared (weight ÷ height²). For example, someone weighing 70kg and 1.73m tall: 70 ÷ (1.73 × 1.73) = 23.4 BMI, which falls in the good healthy weight range.
Is being at the top of the good BMI range (24.9) still healthy?
Yes. A BMI of 24.9 is still within the healthy weight category. Both 18.5 and 24.9 are considered healthy by NHS standards, though where within the range you fall depends on your individual health, fitness, and other factors.
What if I have a good BMI but still feel unhealthy?
BMI is just one measure. If you have a good BMI but feel unwell, consider your waist circumference, fitness level, diet, stress, and sleep. See your GP if you have health concerns — they can assess factors BMI doesn't capture.
How do I know if I should try to move from overweight (25–29.9) into the good BMI range?
If your BMI is in the overweight category, losing 5–10% of your body weight can bring meaningful health benefits. Our weight loss calculator and progress tracker can help you set realistic goals and track progress toward a healthier BMI range.
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.