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
BMI Index: What's a Healthy Range?
The healthy BMI range for most UK adults is 18.5 to 24.9 according to NHS guidelines. BMI (body mass index) is a simple measurement that divides your weight in kilograms by your height in metres squared, giving a screening tool to assess whether you're at a healthy weight. However, if you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends a lower healthy BMI range of 18.5 to 22.9 due to higher health risks at standard thresholds. Use our free BMI calculator above to instantly check where you fall within these ranges.
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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 Ranges
The body mass index formula is: weight (kg) ÷ height (m)². The NHS uses five main BMI categories to classify adults:
- Underweight: BMI below 18.5 — associated with nutritional deficiency and bone health risks
- Healthy weight: BMI 18.5–24.9 — optimal range for most adults
- Overweight: BMI 25.0–29.9 — increased risk of type 2 diabetes and heart disease
- Obese (Class I): BMI 30.0–34.9 — significantly elevated health risks
- Obese (Class II): BMI 35.0–39.9 — high health risks including cardiovascular disease
- Severely obese (Class III): BMI 40.0+ — very high risk requiring medical attention
For adults of South Asian and Black African or Caribbean backgrounds, the overweight bmi threshold starts at 23.0 and obese begins at 27.5, reflecting research showing these populations face elevated diabetes and heart disease risk at lower BMI levels.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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 What Else Matters
While the BMI index is a useful screening tool, it has important bmi limitations. BMI doesn't distinguish between muscle and fat — athletic individuals with high muscle mass may have a high BMI despite low body fat. It also ignores where fat is stored; excess weight around the abdomen (apple shape) carries more health risk than weight distributed elsewhere. Your waist circumference is equally important: men with a waist over 94cm (37 inches) and women over 80cm (31.5 inches) have increased cardiovascular risk, regardless of BMI. Age, ethnicity, and medical history also affect health risk at any given BMI. For personalised advice about what your BMI means for your health, speak with your GP.
- 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 BMI is considered healthy in the UK?
According to NHS guidelines, a healthy BMI is 18.5 to 24.9 for most UK adults. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy range is 18.5 to 22.9. Use our free BMI calculator to check your personal BMI instantly.
Is a BMI of 25 overweight?
Yes. A BMI of 25 falls into the overweight category (25.0–29.9) according to NHS classifications. This range is associated with increased risk of type 2 diabetes and cardiovascular disease, though individual health risk depends on many factors including fitness level and waist circumference.
Can BMI be inaccurate?
Yes. BMI doesn't account for muscle mass, body composition, or where fat is stored. Athletes and very muscular people may have high BMI despite low body fat. Waist measurement and overall fitness are equally important health indicators alongside BMI.
What's the difference between overweight and obese BMI?
Overweight is BMI 25.0–29.9, whilst obese starts at BMI 30.0. The obese category is further divided into Class I (30.0–34.9), Class II (35.0–39.9), and Class III (40.0+), reflecting progressively higher health risks. Your GP can discuss what category means for your individual health.
How do I calculate my BMI from weight in stone?
Convert your weight to kilograms first (divide stone by 0.1575), then divide by your height in metres squared. Alternatively, use our free weight converter and BMI calculator above to get your BMI instantly without a UK pharmacy calculation.
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.