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 the NHS BMI Chart?
The NHS BMI chart is the official UK health standard that categorises adults into weight categories based on their height and weight. It uses the BMI (body mass index) formula to determine whether you fall into a healthy weight range or whether excess weight may affect your health. Unlike other countries, the NHS recognises ethnicity-specific thresholds for people of South Asian, Chinese, Black African, or Black Caribbean heritage due to their higher health risks at lower BMI levels. Understanding your BMI category is a useful first step in assessing your health, though it's important to remember that BMI has limitations and should always be considered alongside other measures like waist circumference.
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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 Healthy Weight Ranges
The NHS BMI formula divides weight (in kilograms) by height (in metres) squared. The standard NHS BMI categories for UK adults are:
- Below 18.5: Underweight
- 18.5 to 24.9: Healthy weight (target range)
- 25.0 to 29.9: Overweight
- 30.0 to 34.9: Obese (Class I)
- 35.0 to 39.9: Obese (Class II)
- 40.0 and above: Severely obese (Class III)
For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy BMI range is lower (18.5 to 22.9), and the overweight threshold starts at BMI 23.0 rather than 25.0. This difference reflects research showing these populations face higher risks of type 2 diabetes and heart disease at the same BMI as white European adults. Use our free BMI calculator above to find your personal BMI instantly and see which category you fall into.
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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.
BMI Limitations and What Else Matters
BMI limitations are important to understand: BMI does not distinguish between muscle and fat, so athletes or very muscular people may have a high BMI despite low body fat percentage. BMI also ignores where fat is stored — abdominal (belly) fat is more closely linked to health risks than fat stored elsewhere. Waist circumference is equally important: the NHS recommends men keep waist measurement below 94cm (37 inches) and women below 80cm (31.5 inches). Your GP can provide personalised guidance about what your BMI means for your individual health, especially if you have underlying medical conditions, take medications, or are pregnant. Remember that healthy weight is about overall health outcomes, not a single number.
- 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 the healthy BMI range according to the NHS?
The NHS defines a healthy BMI as 18.5 to 24.9 for white European adults. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the range is lower: 18.5 to 22.9. Your GP can advise on the most appropriate range for you.
How do I calculate my BMI using the NHS formula?
The formula is: weight in kilograms ÷ (height in metres × height in metres). For example, if you weigh 70kg and are 1.75m tall: 70 ÷ (1.75 × 1.75) = 22.9. Our free BMI calculator on this page does this instantly for you.
What does an overweight BMI threshold mean on the NHS chart?
An overweight BMI threshold starts at 25.0 on the standard NHS chart. For South Asian, Chinese, Black African, or Black Caribbean adults, the threshold is lower at 23.0. This reflects different health risk profiles at the same BMI.
Why are BMI limitations important to know about?
BMI doesn't account for muscle mass, bone density, or where fat is stored. A very muscular person may have a high BMI but be healthy. Waist circumference, fitness level, and blood pressure are equally important. Always discuss your BMI with your GP for personalised advice.
Can I use the NHS BMI chart if I'm pregnant or elderly?
BMI is less accurate during pregnancy and in older adults who have lost muscle mass. If you're pregnant, your midwife will use pregnancy-specific guidelines. If you're elderly or have health concerns, your GP can provide guidance specific to your situation.
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.