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 Test UK: NHS Guidelines and What Your Result Means
A BMI test is a simple health screening tool used by the NHS to assess whether an adult's weight falls within a healthy range for their height. BMI (body mass index) is calculated by dividing your weight in kilograms by your height in metres squared. In the UK, the NHS uses specific BMI categories to help identify whether someone may be at increased health risk. Our free BMI calculator above gives you your personal result instantly, but understanding what that number means — and the NHS guidance behind it — is just as important as knowing the figure itself.
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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 NICE Guidance
The NHS BMI formula is the same worldwide: weight (kg) ÷ height (m)². However, the NHS BMI range UK uses specific categories to assess health risk:
- 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+
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower overweight BMI threshold values — a healthy BMI for these groups is 18.5 to 22.9, with overweight starting at 23.0. This is because these populations face higher cardiovascular and diabetes risk at lower BMI levels. NICE guidance supports using these ethnic-specific BMI categories UK in clinical practice.
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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.
NHS Weight Management Pathway and When to Seek Help
The NHS offers a structured weight management pathway across four tiers. Tier 1 includes self-help resources and community programmes. Tier 2 provides primary care-based behaviour change support through your GP. If your BMI test result shows you are overweight or obese with weight-related health conditions (such as type 2 diabetes, high blood pressure, or heart disease), your GP can refer you to Tier 3 specialist weight management services. Tier 4 covers bariatric surgery for severe obesity. Use our free BMI calculator and weight converter on this page to check your current position, then speak with your GP about which NHS support tier is right for you. Your GP can discuss whether lifestyle changes, behaviour support, or prescription weight loss treatment may be appropriate based on your individual health.
- 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 normal BMI according to the NHS?
According to NHS guidelines, 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 slightly lower healthy range of 18.5 to 22.9, as these groups have higher health risks at the same BMI level.
How do I calculate my BMI test result?
The BMI formula is: weight in kilograms ÷ (height in metres)². For example, if you weigh 70kg and are 1.75 metres tall, your BMI is 70 ÷ (1.75)² = 22.9. Use our free BMI calculator above to get an gradual improvement without a UK pharmacy calculation.
What BMI is considered overweight in the UK?
The NHS defines overweight as a BMI of 25.0 to 29.9. An overweight BMI threshold in the UK starts at 25.0 for most adults, though South Asian and some other ethnic groups have a slightly lower threshold starting at 23.0 according to NHS guidance.
What are the limitations of a BMI test?
BMI limitations include that it cannot 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 (waist circumference matters), and it may be less accurate for elderly people or during pregnancy. Your GP can assess your overall health risk beyond BMI alone.
Should I see my GP about my BMI test result?
If your BMI test shows you are overweight (25.0–29.9) or obese (30.0+), especially if you have weight-related health conditions like diabetes or high blood pressure, it's worth discussing with your GP. They can advise whether NHS weight management support, lifestyle changes, or other interventions may help. Your GP can also consider your ethnic background when interpreting your result.
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.