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 The Normal BMI?
A normal BMI according to NHS guidelines is between 18.5 and 24.9. This range is considered healthy weight for adults and is based on the relationship between your weight and height. BMI (body mass index) is a simple screening tool used by healthcare professionals across the UK to assess whether someone's weight falls within a healthy range. However, it's just one indicator of health — other factors like fitness, muscle mass, and where fat is stored also matter. Use our free BMI calculator above to find out 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 What They Mean
The NHS BMI formula divides your weight in kilograms by your height in metres squared. The resulting number places you into one of five categories:
- Underweight: BMI below 18.5 — may indicate inadequate nutrition
- Healthy weight: BMI 18.5–24.9 — the target range for most adults
- Overweight: BMI 25.0–29.9 — increased health risks begin here
- Obese (Class I): BMI 30.0–34.9 — elevated risk of weight-related conditions
- Severely obese: BMI 40.0 and above — significantly increased health risks
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS BMI range UK thresholds are lower — healthy weight starts at 18.5 but overweight begins at 23.0 instead of 25.0. This reflects higher cardiovascular risk in these populations at lower BMI levels. Your GP can explain which thresholds apply to you.
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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 Complementary Measures
BMI limitations are important to understand. BMI doesn't distinguish between muscle and fat — so athletes with significant muscle mass may have a high BMI despite low body fat. It also ignores where fat is stored; abdominal fat carries greater health risk than fat stored elsewhere. BMI is less accurate for elderly adults (who naturally lose muscle) and during pregnancy.
For a more complete picture of your health, ask your GP about waist circumference measurement. NHS guidelines suggest increased risk if waist circumference exceeds 94cm (37 inches) for men or 80cm (31.5 inches) for women. Combining BMI with waist measurement gives a better assessment than either measure alone. Our free weight converter helps track your weight in the units you prefer.
- 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.
How do I calculate my normal BMI?
Divide your weight in kilograms by your height in metres squared. Example: if you weigh 70kg and are 1.75m tall, your BMI is 70 ÷ (1.75 × 1.75) = 22.9. Use our free BMI calculator above for gradual improvement — it works in both metric and imperial measurements.
Is a BMI of 25 considered normal?
No. A BMI of 25 falls into the overweight category according to NHS guidelines. Normal (healthy weight) is 18.5–24.9. At 25, you're just above the healthy threshold, though individual health depends on many factors beyond BMI alone.
What is the ideal healthy BMI for women?
The same as for men: 18.5–24.9 according to NHS guidelines. However, women of South Asian, Chinese, Black African, or Black Caribbean heritage should aim for 18.5–22.9. Your GP can advise what's ideal for your individual circumstances, considering your age, fitness, and health conditions.
Why is my BMI higher than someone the same height and weight?
This shouldn't happen if you're truly the same height and weight — BMI would be identical. However, if you have more muscle mass (from exercise) and they have more fat, your BMI might feel "wrong" because muscle is denser than fat. This is a key BMI limitation — it's a screening tool, not a body composition measure.
Can I use BMI to check if I'm overweight?
Yes, BMI is useful as a screening tool. The healthy BMI range UK is 18.5–24.9 for most adults. If your BMI is 25 or above, you're classified as overweight or obese. However, always discuss results with your GP, as BMI has limitations and doesn't account for muscle, age, or ethnicity-specific risk factors.
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.