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
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Obese Chart — Understanding Your BMI
If you're wondering whether you're obese, the first step is to calculate your BMI (body mass index). The NHS defines obesity as a BMI of 30 or above, with different class levels depending on how high your BMI is. Use our free BMI calculator above to check your personal BMI instantly — it takes just seconds. Understanding where you fall on the obese BMI scale helps you see what health support might be available to you.
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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 Obese Thresholds
The NHS defines obesity using standard BMI ranges that apply to most UK adults:
- Healthy weight: BMI 18.5–24.9
- Overweight: BMI 25–29.9 — above healthy range but not yet obese
- Obese Class I: BMI 30–34.9 — first level of obesity
- Obese Class II: BMI 35–39.9 — higher risk
- Severely obese (Class III): BMI 40 and above — highest risk category
If you have a BMI of 30 or above, you fall into the obese category. However, important note: if you are of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds — obese BMI for these groups starts at 27.5, because these populations face higher health risks at lower BMI levels.
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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.
Waist Measurement and Next Steps
Your BMI is just one part of the picture. The NHS also recommends checking your waist measurement — where fat is stored matters for health. Men with a waist over 94cm (37 inches) have increased risk; over 102cm (40 inches) is high risk. Women over 80cm (31.5 inches) have increased risk; over 88cm (34.5 inches) is high risk.
If your BMI is 30 or above, speaking to your GP is the next step. They can discuss your individual health, any weight-related conditions, and what support is available — including lifestyle advice, referral to weight management services, or potentially prescription weight loss treatment if eligible. Convert your weight between kg, stone, and lbs using our free weight converter if you need to check your measurements in different units.
- 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 does an obese BMI mean for my health?
A BMI of 30 or above is associated with increased risk of type 2 diabetes, heart disease, high blood pressure, and certain cancers. However, many people with obese BMI live healthily. Your GP can assess your individual risk based on your overall health, not just BMI alone.
Is the obese chart the same for everyone in the UK?
The standard NHS obese BMI (30+) applies to most UK adults. However, people of South Asian, Chinese, Black African, or Black Caribbean heritage should use lower thresholds — obese BMI starts at 27.5 for these groups due to higher health risks at lower weights.
Can I be obese and still be healthy?
BMI does not account for muscle mass, fitness level, or overall health markers. Some people with higher BMI have good blood pressure, cholesterol, and fitness. However, a BMI of 30+ does carry higher statistical health risks, which is why your GP may discuss support options.
What should I do if my BMI shows I'm obese?
Speak to your GP. They can assess your health holistically, discuss any weight-related conditions, and recommend support — which might include diet and exercise advice, referral to NHS weight management services, or prescription treatment if you meet eligibility criteria.
Does waist measurement matter if I already know my BMI?
Yes. Waist measurement indicates where fat is stored, and central (belly) fat carries higher cardiovascular risk than fat distributed elsewhere. Even at the same BMI, someone with a large waist has greater health risk — so your GP may consider both measurements.
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.