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 Category BMI Range?
The obese category starts at a BMI of 30.0 and above according to NHS guidelines. BMI is calculated by dividing your weight in kilograms by your height in metres squared. The obese category is further divided into three classes — Class I (30.0–34.9), Class II (35.0–39.9), and Class III (40.0+) — to reflect increasing health risks. Understanding where your BMI falls within the obese range can help you and your GP discuss appropriate health management options. Use our free BMI calculator above to check your personal BMI instantly.
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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.
Obese BMI Classes and Health Risk Ranges
The obese category BMI range is divided into three classes, each with increasing health risk:
- Obese Class I: BMI 30.0–34.9 — increased health risks
- Obese Class II: BMI 35.0–39.9 — high health risks
- Obese Class III: BMI 40.0 and above — very high health risks (also called severe or morbid obesity)
According to NHS guidelines, a healthy BMI is 18.5–24.9. The overweight BMI threshold begins at 25.0. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the healthy BMI range is lower (18.5–22.9), and the obese category may start at a lower BMI due to higher cardiovascular risk at the same weight. You can verify your BMI range using the weight converter and BMI calculator on this page.
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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 Other Health Measures
The BMI formula is useful for screening but has important limitations. It does not distinguish between muscle and fat — athletes may have a high BMI despite low body fat. BMI also does not account for where fat is stored; excess fat around the waist carries greater health risk than fat elsewhere. The bmi limitations mean it should be used alongside other measures. Your GP may also assess your waist circumference (over 102cm in men or 88cm in women indicates increased risk), blood pressure, and cholesterol levels. These factors together give a fuller picture of your health than BMI 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.
What BMI number counts as obese?
According to NHS guidelines, a BMI of 30.0 and above is classified as obese. This is divided into three classes: Class I (30.0–34.9), Class II (35.0–39.9), and Class III (40.0+). For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the threshold may be lower due to higher health risks at similar BMI levels.
Is a BMI of 32 considered obese?
Yes. A BMI of 32 falls within Obese Class I (30.0–34.9) according to NHS categories. This indicates increased health risks compared to the healthy BMI range (18.5–24.9). Your GP can discuss personalised health management options with you.
What health risks are associated with the obese BMI category?
Obesity increases risk of type 2 diabetes, cardiovascular disease, high blood pressure, certain cancers, sleep apnoea, osteoarthritis, and fatty liver disease. The risk increases as BMI rises into Classes II and III. Even a modest 5–clinically studied weight loss can improve many of these conditions.
How do I know if my BMI falls in the obese range?
Use our free BMI calculator on this page — enter your height and weight, and it will instantly show your BMI and category. Alternatively, divide your weight in kilograms by your height in metres squared. If the result is 30 or above, you are in the obese category.
Does muscle affect BMI in the obese category?
Yes. BMI doesn't distinguish between muscle and fat, so very muscular individuals may have a high BMI without excess body fat. This is a key BMI limitation. If you're very muscular, your GP can assess your health using waist measurement, blood pressure, and other factors 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.