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 BMI Normative Data and Why Does It Matter?
Normative data for BMI refers to the standard weight ranges and categories used to assess whether an adult's weight is healthy for their height. In the UK, the NHS uses established BMI thresholds to categorise adults into underweight, healthy weight, overweight, and obese categories. Understanding these normative ranges helps you assess your own health status and identify whether lifestyle changes or medical support might be beneficial. Use our free BMI calculator above to check where your personal measurements fall within these established guidelines.
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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 for UK Adults
The BMI formula is straightforward: weight in kilograms divided by height in metres squared. The resulting number places you into one of five standard categories recognised by the NHS:
- Underweight: BMI below 18.5
- Healthy weight: BMI 18.5–24.9
- Overweight: BMI 25.0–29.9
- Obese (Class I): BMI 30.0–34.9
- Severely obese (Class II/III): BMI 35.0+
These bmi categories uk are based on epidemiological data showing increased health risks at each threshold. For most UK adults, a healthy BMI between 18.5 and 24.9 is associated with the lowest risk of weight-related health conditions including type 2 diabetes, cardiovascular disease, and certain cancers. However, bmi range uk thresholds are not one-size-fits-all — ethnicity, age, and muscle mass all influence what your individual healthy range should be.
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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 Complementary Health Measures
While the bmi calculator is a useful screening tool, BMI has important limitations. It does not distinguish between muscle and fat — athletes may have a high BMI but low body fat percentage. BMI also does not account for where fat is stored; waist circumference is an equally important health marker. The NHS bmi guidelines recommend measuring waist as well: men over 94cm (37 inches) and women over 80cm (31.5 inches) face increased health risk regardless of BMI. For a complete picture of your health, ask your GP to assess your waist measurement, blood pressure, cholesterol, and blood sugar alongside your BMI.
- 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 are ethnicity-adjusted BMI thresholds in the UK?
For adults of South Asian, Chinese, Black African, and Black Caribbean heritage, the NHS recommends lower BMI thresholds because these groups face higher cardiovascular and diabetes risk at lower weights. Healthy weight for these populations is BMI 18.5–22.9, overweight is 23.0–27.4, and obese is 27.5+. Your GP can advise whether adjusted thresholds apply to you.
Is BMI accurate for elderly adults or very muscular people?
No. BMI is less accurate for older adults due to age-related muscle loss, and for athletes or very muscular individuals because it cannot distinguish muscle from fat. Your GP may use additional assessments like body composition analysis or waist-to-hip ratio for these groups.
What healthy weight range should I aim for at my height?
Calculate your healthy weight range using the formula: lower bound = 18.5 × height(m)², upper bound = 24.9 × height(m)². For example, at 1.73m (5ft 8in), healthy weight is 55–74kg (8st 10lbs–11st 10lbs). Use our free BMI calculator to find your personalised range in seconds.
How does BMI relate to waist circumference and health risk?
You can have a "healthy" BMI but still carry excess visceral fat around your abdomen, which increases disease risk. Conversely, some people with slightly elevated BMI may be healthy if most weight is muscle. The NHS recommends assessing both BMI and waist circumference for a complete health picture.
What is the average BMI for UK adults, and how has it changed?
Current Office for National Statistics data shows the average UK adult BMI is approximately 27.5–28, falling in the "overweight" category. Average BMI has increased significantly over the past two decades, reflecting wider trends in sedentary behaviour and calorie-dense food availability across the population.
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.