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 Are the NHS BMI Ranges?
The NHS uses standardised BMI ranges to categorise adult weight and health risk. BMI (body mass index) is calculated by dividing your weight in kilograms by your height in metres squared. Understanding where your BMI falls within the official NHS categories helps you assess whether your weight is healthy for your height. These ranges form the foundation of UK weight management guidance and are used across the NHS to identify who may benefit from weight loss support or specialist services.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 uses metric measurements: BMI = weight (kg) ÷ height (m)². The official NHS BMI range categories are:
- 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
A healthy BMI of 18.5–24.9 is the target range for most UK adults. However, for people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds — a healthy range starts at 18.5 but extends only to 22.9, with the overweight BMI threshold starting at 23.0. Use our free BMI calculator above to find your personal BMI instantly and see which BMI category UK you fall into based on your height and weight.
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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 Other Important Measures
While BMI is a useful screening tool, it has important BMI limitations. BMI does not distinguish between muscle and fat — athletes or very muscular individuals may have a high BMI but low body fat. BMI also ignores where fat is stored; excess fat around the stomach carries greater health risk than fat stored elsewhere. For older adults, muscle naturally decreases with age, which can skew BMI interpretation. The NHS recommends measuring waist circumference alongside BMI: men over 94cm (37 inches) or women over 80cm (31.5 inches) have increased health risk, regardless of BMI. Your GP can assess your individual health context and recommend whether lifestyle changes, weight loss support, or specialist services may help.
- 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 a healthy BMI range in the UK?
According to NHS guidance, a healthy BMI for most UK adults is between 18.5 and 24.9. However, for people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends a healthy BMI of 18.5 to 22.9, as these groups face higher health risks at higher BMI levels.
How do I calculate my BMI using the NHS method?
The NHS BMI formula is: weight (kg) ÷ height (m)². For example, someone weighing 70kg and 1.75m tall would have a BMI of 70 ÷ (1.75 × 1.75) = 22.9. Our free BMI calculator on this page does this instantly — just enter your weight and height.
What BMI indicates I am overweight?
An overweight BMI threshold starts at 25.0 and goes up to 29.9 according to NHS categories. However, for South Asian and other specified ethnic backgrounds, the overweight range begins at 23.0. Use our weight converter and BMI calculator together to find your exact BMI and category.
Is BMI a perfect measure of health?
No — BMI has limitations. It does not account for muscle mass, bone density, or where fat is stored on your body. The NHS recommends using BMI alongside waist circumference measurement and consulting your GP about your overall health, not BMI alone.
What should I do if my BMI is above the healthy range?
If your BMI is above 24.9 (or 22.9 for certain ethnic groups), speak to your GP. Small changes to diet and physical activity can help. The NHS offers weight management programmes through primary care, and specialist services are available if needed. Track your progress with our free progress tracker.
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.