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 Obese BMI Range?
An obese BMI range in the UK starts at 30.0 and above according to NHS guidelines. Obesity is divided into three classes: Class I (30.0–34.9), Class II (35.0–39.9), and Class III or severe obesity (40.0+). However, if you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds—obesity may begin at 27.5. Understanding where your weight falls helps you discuss health options with your GP and make informed decisions about your wellbeing.
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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 Obesity Categories and BMI Ranges
The NHS BMI categories classify obesity into three distinct classes. A BMI of 30.0 to 34.9 is Class I obesity, 35.0 to 39.9 is Class II obesity, and 40.0 and above is Class III (severe) obesity. Each class carries increasing health risks. To calculate your personal BMI, divide your weight in kilograms by your height in metres squared (BMI = weight ÷ height²). For example, an adult weighing 90kg (14st 2lbs) who is 1.75m tall has a BMI of approximately 29.4 (overweight category), while at 100kg (15st 10lbs) they would have a BMI of 32.7 (Class I obesity). Use our free BMI calculator above to check your personal BMI instantly and see which category you fall into.
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy BMI range is 18.5–22.9, overweight is 23.0–27.4, and obesity begins at 27.5. This adjustment reflects that these populations face higher cardiovascular and type 2 diabetes risk at lower BMI levels compared to other groups.
Clinically BackedWeight Loss
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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
While BMI is a useful screening tool, it has important limitations. BMI does not distinguish between muscle and fat—athletes may have a high BMI but low body fat percentage. BMI also doesn't account for where fat is stored; excess weight around the waist carries greater health risk than fat distributed elsewhere. Age, bone density, and muscle mass all affect how BMI relates to actual health risk.
The NHS recommends checking waist circumference alongside BMI. For men, a waist over 94cm (37in) indicates increased risk; over 102cm (40in) indicates high risk. For women, over 80cm (31.5in) is increased risk; over 88cm (34.5in) is high risk. If you're concerned about your weight and health, discuss your individual situation with your GP, who can assess your complete health picture and suggest appropriate next steps, which may include lifestyle changes or referral to specialist weight management services.
- 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.
Is a BMI of 30 definitely obese?
Yes, according to NHS guidelines, a BMI of 30.0 and above is classified as obese (Class I). However, this is a screening tool only. Your GP should assess your overall health, waist circumference, and other factors to determine actual health risk. BMI doesn't account for muscle mass or fat distribution.
What health risks come with an obese BMI?
Obesity (BMI 30+) increases risk of type 2 diabetes (significantly higher at severe obesity), heart disease, high blood pressure, certain cancers, sleep apnoea, osteoarthritis, and fatty liver disease. Even a modest 5–clinically studied weight loss can improve many of these conditions.
Do different ethnic groups have different obese BMI ranges?
Yes. The NHS recommends lower BMI thresholds for people of South Asian, Chinese, Black African, and Black Caribbean heritage because these groups have higher cardiovascular and metabolic disease risk at lower BMI levels. For these groups, obesity may begin at BMI 27.5 rather than 30.
How is obesity BMI range different from overweight?
Overweight in the UK is a BMI of 25.0–29.9, whilst obesity starts at 30.0. Obesity is further divided into three classes (I, II, and III/severe). These are NHS clinical categories used to assess health risk and determine what interventions might be appropriate.
Can I lose weight if my BMI is in the obese range?
Yes. The NHS recommends losing weight at 0.5–1 kg (1–2 lbs) per week through a combination of balanced eating and physical activity. Specialist weight management services, available through the NHS or privately, can provide support. Prescription weight loss medications are available for eligible adults—your GP can assess whether this is appropriate 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.