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 a Healthy BMI Range?
A healthy BMI range according to NHS guidelines is between 18.5 and 24.9 for most UK adults. However, if you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends a lower healthy BMI range of 18.5 to 22.9, as these populations face higher health risks at higher BMI levels. Your BMI (body mass index) is a screening tool that helps assess whether your weight falls into a healthy range for your height. Use our free BMI calculator above to check your personal BMI instantly and see where you fall within these guidelines.
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 BMI formula is simple: weight (kg) divided by height (m) squared. Using this calculation, the NHS has established clear BMI categories uk standards that apply to most adults:
- Underweight: BMI below 18.5
- Healthy weight (healthy BMI): BMI 18.5–24.9
- Overweight: BMI 25.0–29.9
- Obese (Class I): BMI 30.0–34.9
- Obese (Class II): BMI 35.0–39.9
- Severely obese (Class III): BMI 40.0+
For adults of South Asian, Chinese, Black African, or Black Caribbean backgrounds, lower thresholds apply: healthy BMI is 18.5–22.9, and the overweight BMI threshold begins at 23.0. This reflects clinical evidence that these groups develop weight-related health conditions at lower BMI levels. If you're unsure which category applies to you, calculate your BMI using the calculator on this page to get your exact reading.
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 Why Other Measures Matter
While BMI is a useful screening tool, it has important BMI limitations: it cannot distinguish between muscle and fat, so athletes or very muscular people may have a high BMI despite low body fat. BMI also doesn't account for where fat is stored — belly fat (visceral fat) is more harmful to health than fat stored elsewhere. For a more complete picture of health, the NHS recommends also measuring your waist circumference. A healthy waist is under 94cm (37 inches) for men and under 80cm (31.5 inches) for women; over these limits indicates increased health risk. Age, bone density, and individual health conditions also matter. Your GP can discuss what a healthy weight means for you personally.
- 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 NHS guidance?
The NHS recommends a healthy BMI of 18.5–24.9 for most UK adults. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy range is lower at 18.5–22.9 due to higher health risks at elevated BMI levels in these populations.
How do I calculate my BMI?
Use the BMI formula: weight in kilograms divided by height in metres squared. For example, if you weigh 70kg and are 1.75m tall: 70 ÷ (1.75 × 1.75) = BMI of 22.9. Our free BMI calculator above does this instantly — just enter your weight and height.
Why are there different healthy BMI ranges for different ethnicities?
Research shows that South Asian, Chinese, Black African, and Black Caribbean adults develop type 2 diabetes, heart disease, and other weight-related conditions at lower BMI levels than white European populations. The NHS reflects this evidence with adjusted thresholds to better identify health risk in these groups.
What should I do if my BMI is outside the healthy range?
If your BMI is outside 18.5–24.9, speak to your GP. They can assess your overall health, discuss whether weight change is appropriate for you, and suggest support options including lifestyle changes, dietary advice, or specialist services if needed.
Is BMI the only measure of a healthy weight?
No. BMI is a screening tool but has limitations — it doesn't account for muscle mass, where fat is stored, or individual health conditions. Waist circumference, fitness level, and blood pressure are also important. Your GP can give you personalised advice about what healthy weight means for you.
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.