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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BMI Check NHS — Understanding Your BMI According to UK Health Guidelines
A BMI check using NHS guidelines helps you understand whether your weight falls into a healthy range for your height. The NHS uses standardised BMI categories to assess weight status across UK adults, though these thresholds vary for certain ethnic groups. Use our free BMI calculator above to check your personal BMI instantly, or read on to understand what the NHS categories mean and when you should speak to your GP about weight management support.
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 What They Mean
The NHS uses five main BMI categories to classify weight status in UK adults. A healthy BMI according to NHS guidance falls between 18.5 and 24.9. Overweight is classified as BMI 25.0 to 29.9, while obesity begins at BMI 30.0 and above, with further subdivisions into Class I (30.0–34.9), Class II (35.0–39.9), and Class III or severe obesity (40.0+).
However, the NHS recognises that BMI alone has limitations. It does not distinguish between muscle and fat — athletes may have a high BMI but low body fat. The formula also does not account for where fat is stored around the body, which matters for health risk. That's why the NHS also recommends checking your waist circumference: men should aim for under 94cm (37 inches), and women under 80cm (31.5 inches). For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds due to higher disease risk at lower weights.
To find your healthy weight range for your height, use our weight converter alongside the BMI calculator on this page.
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 offers a structured weight management pathway across four tiers. Tier 1 includes self-help and community programmes like the NHS Weight Loss Plan available online. Tier 2 involves your GP and local behaviour change services. Tier 3 is specialist multidisciplinary weight management services, where prescription weight loss medications like Mounjaro or Wegovy may be discussed. Tier 4 covers bariatric surgery for severe obesity with significant health complications.
You should speak to your GP if your BMI is 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Your GP can assess your individual health and refer you to appropriate NHS support. Waiting times for specialist services vary significantly by region, so starting with your GP is the first step.
- 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 healthy BMI according to the NHS?
The NHS defines a healthy BMI as between 18.5 and 24.9 for most UK adults. However, for people of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy range is 18.5 to 22.9 due to higher health risks at higher BMI levels. Your GP can advise what's healthy for you personally.
Why do different ethnic groups have different NHS BMI thresholds?
Research shows that people from South Asian, Chinese, Black African, and Black Caribbean backgrounds develop weight-related health conditions like type 2 diabetes and cardiovascular disease at lower BMI levels than white Europeans. The NHS adjusted thresholds reflect this increased risk, ensuring earlier intervention and better health outcomes for these groups.
Does a high BMI always mean I'm unhealthy?
Not necessarily. BMI does not distinguish between muscle and fat, so athletes or very muscular individuals may have a high BMI but good health. However, BMI remains a useful screening tool. The NHS also recommends measuring waist circumference and considering overall health markers. Your GP can assess your individual health status.
When should I see my GP about my BMI?
Contact your GP if your BMI is 30 or above, or 27–29.9 with weight-related conditions like diabetes, high blood pressure, or sleep apnoea. Your GP can discuss weight management options, including lifestyle changes and potentially referral to specialist services. Early action often leads to better outcomes.
What happens if my GP refers me to NHS weight management services?
NHS weight management services are typically provided through tier 3 specialist multidisciplinary teams. They offer structured programmes combining behaviour change support, dietary guidance, and physical activity advice. Prescription weight loss medications may be considered if appropriate following clinical assessment. Availability and waiting times vary by region.
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.