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 an NHS BMI Check?
An NHS BMI check is a simple health screening tool used by the NHS to assess whether your weight falls within a healthy range for your height. BMI (Body Mass Index) uses a standard formula to calculate your body weight category, helping identify potential health risks. The NHS uses BMI as a starting point for weight health discussions, though it's important to understand that BMI alone doesn't tell the complete health picture. You can check your BMI instantly using our free BMI calculator above, or learn how to calculate it manually below.
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 Healthy Weight Ranges
The NHS BMI formula is straightforward: weight (kg) ÷ height (m)². The resulting number places you into one of five BMI categories used across the UK:
- Below 18.5: Underweight
- 18.5 to 24.9: Healthy weight (the recommended healthy BMI range
- 25.0 to 29.9: Overweight
- 30.0 to 34.9: Obese (Class I)
- 35.0 and above: Severely obese
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds: a healthy BMI starts at 18.5 but extends only to 22.9, with the overweight BMI threshold beginning at 23.0. This reflects evidence that these populations face higher health risks at lower BMI levels. Use our free BMI calculator to check your personal BMI instantly and see which category you fall into.
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.
BMI Limitations and What Else Matters
BMI limitations are important to understand. BMI does not distinguish between muscle and fat — athletes or very muscular individuals may have a high BMI despite low body fat. It also doesn't account for age, bone density, or where fat is stored on your body. The NHS recognises these BMI limitations and therefore always considers additional factors when assessing weight health. Waist circumference is equally important: men should aim for under 94cm (37 inches) and women under 80cm (31.5 inches). Your GP can discuss your individual health picture, not just your BMI number. Use the weight converter on this page to check your weight in different units, and remember that your overall health depends on diet, physical activity, sleep, and stress as much as weight alone.
- 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.
How do I calculate my BMI using the NHS formula?
Divide your weight in kilograms by your height in metres squared. For example, if you weigh 70kg and are 1.75m tall: 70 ÷ (1.75 × 1.75) = 70 ÷ 3.06 = 22.9 BMI. Our free BMI calculator above does this instantly — just enter your weight and height.
What BMI is considered healthy according to the NHS?
The NHS recommends a healthy BMI between 18.5 and 24.9 for most adults. However, for people of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy range is 18.5 to 22.9. Your GP can advise on what's healthy for you individually.
Can BMI be inaccurate?
Yes. BMI doesn't distinguish between muscle and fat, so athletes may show high BMI despite being healthy. It also ignores where fat is stored and doesn't account for age or bone density. The NHS always considers waist circumference and overall health too, not BMI alone.
What should I do if my BMI falls in the overweight category?
A BMI in the overweight range (25.0–29.9) doesn't automatically mean poor health, especially with good fitness levels. However, the NHS recommends discussing your weight with your GP. Small lifestyle changes — increased physical activity and balanced diet — can help. Your GP can advise on next steps.
How is the NHS BMI check different from private BMI assessments?
NHS BMI checks follow official NHS guidelines and categories. Your GP uses BMI as one screening tool alongside other health measures. Private assessments may offer additional measurements like waist-to-height ratio or body composition analysis, providing a more detailed picture alongside BMI.
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.