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
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What Is BMI With Percentile?
BMI with percentile is a way of measuring where your weight sits compared to the wider population. Whilst a standard BMI formula gives you a number and category, percentile ranking shows how your BMI compares to others of the same age and sex. The NHS uses both BMI categories and percentile data when assessing weight-related health risks. Understanding percentiles helps clarify whether your weight is typical for your demographic, which matters because health risks vary across age groups and between men and women. You can check your personal BMI using our free BMI calculator above, which will also show you how your result compares to UK health standards.
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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.
BMI Percentile Ranges and What They Mean
Percentiles divide the population into 100 equal groups, ranked from lowest to highest. A 50th percentile BMI means your weight is exactly average for your age and sex — half the population has a lower BMI, half higher. A 75th percentile BMI means you're heavier than 75% of your peer group. A 95th percentile BMI indicates you're among the heavier 5% of your demographic.
For adults, the NHS BMI range provides the primary framework, but percentile data becomes especially important in clinical assessment. Your GP might reference percentiles when discussing cardiovascular risk, diabetes screening, or weight management options. The NHS BMI categories (healthy weight 18.5–24.9, overweight 25.0–29.9, obese 30.0+) apply universally across adults, but percentile context helps personalise health guidance. For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds apply, meaning percentile rankings at your demographic level may indicate earlier intervention points.
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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.
Percentiles vs. Standard BMI Categories — Key Differences
Standard BMI categories UK use fixed cutoff points: everyone with a BMI of 30 or above is classified as obese, regardless of age or gender. Percentiles, by contrast, are relative — they compare your individual result to your specific age and sex group. A BMI of 26 might fall into the 60th percentile for a 45-year-old man but the 75th percentile for a 25-year-old woman, because average weights differ significantly across age groups.
The BMI limitations exist for both approaches: neither accounts for muscle mass, bone density, ethnicity-specific health risks, or where fat is stored. Percentiles can mask health risks in populations where average BMI has risen significantly. This is why your GP uses BMI as a screening tool alongside other measures — waist circumference, blood pressure, cholesterol, and blood glucose — rather than as a standalone diagnosis. Use our free BMI calculator to find your BMI category and see how it aligns with NHS health standards for your height.
- 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.
Are percentiles used by the NHS in the UK?
Yes. The NHS uses BMI percentiles alongside standard categories when assessing weight-related health risk, particularly in clinical settings. Percentiles provide additional context about where your weight sits within your demographic, helping GPs personalise health recommendations. However, standard BMI categories remain the primary framework for initial screening.
What percentile is considered healthy weight?
There is no single "healthy" percentile — it depends on your age and sex. Generally, percentiles between the 10th and 85th suggest your weight is within typical range for your demographic. However, health risk is determined by BMI category (18.5–24.9 is healthy) rather than percentile alone. Your GP can advise what's healthy for you personally.
Does percentile BMI differ for men and women?
Yes. Men and women typically have different average BMIs and body compositions at the same age. A BMI of 26 may rank differently on the percentile scale for men versus women. This is why age- and sex-specific percentile data is more informative than absolute BMI figures alone.
How is BMI percentile calculated?
BMI percentile is calculated by comparing your individual BMI against population data for your age and sex group, then determining what percentage of that group falls below your BMI. For example, if your percentile is 70th, 70% of people your age and sex have a lower BMI. The standard BMI formula (weight in kg ÷ height in metres²) is the same; percentile ranking is the comparison layer.
Should I focus on my BMI percentile or my BMI category?
Both are useful. Your BMI category (from the BMI formula) tells you whether you're in a health risk range according to NHS guidelines. Your percentile provides context about whether your weight is typical for your peer group. For health decisions, focus on your BMI category and speak to your GP about what it means for your individual health.
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