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 Average BMI in the UK?
The average BMI for UK adults is approximately 27.4 for women and 27.9 for men, according to the latest Office for National Statistics data. This means most UK adults are technically overweight or approaching obesity according to NHS BMI guidelines. However, average doesn't mean healthy — understanding your personal BMI and where it falls within the NHS-recommended healthy range is far more important than comparing yourself to national averages. Your individual health depends on your specific circumstances, not population statistics.
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 Healthy Range
According to NHS guidelines, here are the standard BMI categories for UK adults:
- 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
Since the UK average BMI of 27–28 falls in the overweight category, this reflects broader population health trends. However, the NHS-recommended healthy BMI range is 18.5 to 24.9. It's worth noting that for adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds — healthy weight begins at BMI 18.5 to 22.9 for these groups, as they face higher cardiovascular and diabetes risk at lower BMI levels. Use our free BMI calculator above to find your personal BMI instantly.
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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 What Else Matters
While BMI is a useful screening tool, it has important limitations. The BMI formula (weight in kg divided by height in metres squared) doesn't distinguish between muscle and fat — athletes may have a high BMI but low body fat. BMI also doesn't account for where fat is stored, which matters for health risk. Waist circumference is actually a better predictor of cardiovascular risk: the NHS recommends men keep waist circumference under 94cm (37 inches) and women under 80cm (31.5 inches). Age, ethnicity, medical history, and fitness level all affect what a healthy weight means for you. Your GP can provide personalised guidance based on your full health picture, not just your BMI number.
- 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.
Is an average BMI of 27–28 actually a problem?
Not necessarily on its own, but it does mean most UK adults are technically overweight. Being overweight increases risk of type 2 diabetes, heart disease, and joint problems. However, individual health varies — fitness level, diet, genetics, and lifestyle matter too. Your GP can assess whether weight management would benefit your personal health.
Why is the average BMI higher in the UK than some other countries?
The UK average reflects a combination of factors: portion sizes, reduced physical activity, sedentary work, ultra-processed food availability, and lifestyle changes over recent decades. Similar trends exist across most developed nations. Public Health England and the NHS recognise this as a significant health challenge.
What's a good BMI target for me?
The NHS healthy BMI range is 18.5 to 24.9 for most adults, or 18.5 to 22.9 for South Asian, Chinese, Black African, or Black Caribbean adults. However, "healthy" varies by individual — your GP can advise based on your age, medical history, fitness, and overall health. Losing even 5–10% of body weight can significantly improve health markers.
How is BMI calculated, and can I check mine?
BMI formula: weight (kg) ÷ height (m)². For example, someone weighing 75kg and 1.73m tall would have a BMI of 25.1 (overweight category). Our free BMI calculator on this page does this instantly — just enter your height and weight.
Should I worry if my BMI is above average but I feel healthy?
Feeling healthy is important, but BMI and other health markers like blood pressure, cholesterol, and blood sugar matter too. You might feel fine at a higher BMI but still have increased disease risk. A check-up with your GP can assess your actual health status beyond how you feel day-to-day.
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.