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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What BMI Is Considered Obese According to NHS Guidelines
According to NHS guidance, a BMI of 30 or above is classified as obese. However, the specific threshold can vary depending on your ethnic background, as the NHS recommends lower BMI thresholds for people of South Asian, Chinese, Black African, and Black Caribbean heritage due to higher health risks at lower weights. Understanding your BMI range is an important first step in assessing your health, though BMI is just one tool and has limitations. Use our free BMI calculator above to check your personal BMI instantly and see where you fall within the NHS categories.
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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 Obesity Classification
According to NHS guidance, obesity is defined as a BMI of 30 or above. The NHS uses these standard BMI categories for most adults:
- Underweight: BMI below 18.5
- Healthy weight: 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 and above
However, for adults of South Asian, Chinese, Black African, or Black Caribbean descent, the NHS recommends lower thresholds because these groups face higher risks of type 2 diabetes and cardiovascular disease at the same BMI. For these populations, obesity classification begins at a BMI of 27.5 and above, with a healthy weight range of 18.5–22.9. The BMI formula itself is straightforward—weight in kilograms divided by height in metres squared—but understanding your individual risk requires considering your ethnic background, waist circumference, and overall health context.
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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.
NHS Weight Management Support and When to Seek Help
If your BMI falls in the obese range, the NHS offers support through its structured weight management pathway. Most people start with Tier 1 services—self-help resources and community programmes—but if you have health complications linked to excess weight, your GP may refer you to a specialist Tier 3 weight management service. These services provide tailored support including dietary advice, physical activity plans, and prescription weight loss medications where clinically appropriate. Regional availability varies, and waiting times can be long in some areas. It's important to note that BMI alone doesn't determine health risk; waist circumference, fitness level, and existing health conditions all matter. Contact your GP to discuss your personal situation and what support is available in your area.
- 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 exact BMI number that counts as obese?
According to NHS guidelines, a BMI of 30.0 or above is classified as obese. However, for people of South Asian, Chinese, Black African, or Black Caribbean heritage, obesity classification begins at BMI 27.5 and above due to higher health risks at lower weights.
Does BMI have limitations I should know about?
Yes. BMI doesn't distinguish between muscle and fat, so athletes may have a high BMI but low body fat. It also doesn't account for where fat is stored or age-related muscle loss. Always use BMI alongside other measures like waist circumference and discuss your health with your GP.
What should I do if my BMI shows I'm obese?
Contact your GP to discuss your health. They can assess your overall health picture, check for weight-related conditions, and refer you to NHS weight management services if appropriate. Your GP may recommend lifestyle changes, community programmes, or specialist support depending on your individual circumstances.
Can I use the NHS healthy weight range for any height?
Yes. For any height, a healthy BMI is 18.5–24.9 for most adults, or 18.5–22.9 for South Asian, Chinese, Black African, or Black Caribbean adults. Calculate your personal healthy weight range using our free BMI calculator above.
How does waist circumference relate to the obesity BMI threshold?
Waist circumference is an important independent measure of health risk. The NHS recommends that for men, a waist over 94cm (37 inches) indicates increased risk and over 102cm (40 inches) indicates high risk. For women, increased risk starts at 80cm (31.5 inches) and high risk at 88cm (34.5 inches), regardless of 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.