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 Normative Data — What NHS Guidelines Show
BMI normative data refers to the typical weight and health ranges that NHS and public health research have established for UK adults. Understanding these benchmarks helps you see where your own BMI falls within the population and what health outcomes are associated with different ranges. The NHS uses specific BMI categories to assess weight status and health risk, with thresholds adjusted for certain ethnic groups who face higher health risks at lower body weights. Use our free BMI calculator above to find your personal BMI and see how it compares to these normative ranges.
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 Population Benchmarks
The NHS BMI formula divides weight (kg) by height (m)² to produce a single figure that indicates weight status. The standard healthy BMI range for UK adults is 18.5 to 24.9, which NHS evidence shows is associated with the lowest health risks. An overweight BMI threshold begins at 25.0, while obesity begins at 30.0.
- Underweight: BMI below 18.5 — may indicate nutritional concerns
- Healthy weight: BMI 18.5–24.9 — optimal health profile
- Overweight: BMI 25.0–29.9 — increased health risks
- Obese (Class I): BMI 30.0–34.9 — significant health risks
- Obese (Class II): BMI 35.0–39.9 — higher health risks
- Severely obese (Class III): BMI 40.0+ — substantial health risks
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, NICE guidance recommends lower thresholds because research shows these groups face higher diabetes and cardiovascular risk at the same BMI levels as White Europeans.
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.
NHS Weight Management Pathway and When to Seek Help
The NHS recognises that BMI limitations exist — BMI does not distinguish between muscle and fat, nor does it account for where fat is stored. However, BMI remains a useful screening tool for population health. If your BMI falls outside the healthy range, your GP can offer support through the NHS weight management pathway: tier 1 (self-help tools and community programmes), tier 2 (primary care interventions), tier 3 (specialist weight management services), and tier 4 (bariatric surgery for severe cases). Your GP can discuss your individual health risks, comorbidities, and whether interventions like lifestyle change programmes or prescription weight loss medication might be appropriate for you. Even modest weight loss of 5–10% can significantly improve health outcomes.
- 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 considered a healthy BMI according to NHS guidelines?
The NHS defines a healthy BMI as 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 slightly lower: 18.5 to 22.9. These adjusted thresholds reflect research showing these groups have higher health risks at higher BMI levels.
What are the main limitations of BMI as a health measure?
BMI does not distinguish muscle from fat — athletes may have high BMI but low body fat. It also ignores where fat is stored (waist circumference matters for health risk) and may be less accurate for elderly people due to age-related muscle loss. Use our free BMI calculator alongside waist measurement and GP assessment for a complete picture.
At what BMI does the NHS consider someone overweight?
According to NHS guidelines, BMI of 25.0 to 29.9 falls into the overweight category. An overweight BMI indicates increased health risks compared to the healthy range, though risks escalate further at obesity thresholds (30.0+).
Should I be concerned if my BMI is just above 25?
A BMI between 25 and 30 is classified as overweight and warrants attention to diet and activity levels. However, other factors matter too — waist circumference, blood pressure, and blood sugar control all contribute to health risk. Your GP can assess your individual risk profile and advise whether lifestyle changes or further support would be helpful.
How do NHS specialists use BMI normative data in weight management?
NHS tier 3 and tier 4 weight management services use BMI normative data as part of a comprehensive health assessment. They consider your BMI category alongside comorbidities (diabetes, heart disease, sleep apnoea) to determine eligibility for interventions like behaviour change programmes or prescription weight loss medication. Individual health context always takes priority over BMI alone.
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.