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
Understanding Obese Categories in the UK
Obesity is classified into categories based on BMI to help identify health risks. In the UK, the NHS uses standardised BMI ranges to define what constitutes obese, with three separate classes depending on severity. Understanding which obese category you fall into is important because it helps predict health risks and determines eligibility for weight management support. If you're concerned about your weight, use our free BMI calculator above to check where you stand on the NHS health scale.
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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 Obese Categories and Health Implications
The NHS defines obesity as a BMI of 30 or above. This is further divided into three categories:
- Class I (Obese): BMI 30.0–34.9 — increased health risks including type 2 diabetes and high blood pressure
- Class II (Obese): BMI 35.0–39.9 — substantial health risks; weight-related conditions are more common
- Class III (Severely obese): BMI 40.0 and above — very high risk of serious health complications
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds apply due to higher cardiovascular risk at the same BMI. For these groups, obesity begins at BMI 27.5 rather than 30. The obese bmi uk categories help GPs and healthcare professionals assess whether intervention or specialist referral is needed. Even modest weight loss of 5–10% can reduce health risks significantly.
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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.
Health Conditions Linked to Excess Weight
Being in an obese category increases the risk of several serious health conditions. These include type 2 diabetes (risk increases dramatically at higher BMI levels), cardiovascular disease, certain cancers, obstructive sleep apnoea, and non-alcoholic fatty liver disease. Joint pain and mobility problems are also common. Additionally, research shows that waist measurement is an important health indicator alongside BMI — a waist over 94 cm (37 inches) in men or 80 cm (31.5 inches) in women indicates increased cardiovascular risk. Your GP can provide personalised health advice based on your individual circumstances, medical history, and weight status.
- 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 difference between overweight and obese categories?
Overweight is a BMI of 25.0–29.9, whilst obese categories start at BMI 30.0. The NHS uses BMI ranges to classify weight status. Use our free BMI calculator to find your personal BMI and understand where you fall on the healthy weight range scale. For ethnic minorities with adjusted thresholds, the boundaries are lower.
Am I overweight or obese if my BMI is 28?
A BMI of 28 falls in the overweight category (BMI 25.0–29.9) according to NHS guidelines, not obese. However, health risk depends on many factors including fitness level, waist circumference, and medical history. Your GP can assess your individual health and discuss whether lifestyle changes or support would be beneficial for you.
What health support is available if I'm in an obese category?
The NHS offers a structured weight management pathway. Start with your GP, who can refer you to tier 2 or tier 3 specialist weight management services. These services provide behaviour change support, diet advice, and may include prescription weight loss medication if you meet eligibility criteria. Prescription options are available through NHS specialist services or private online prescribers.
Can prescription weight loss medication help if I'm obese?
Adults in obese categories may be eligible for prescription weight loss injections like Mounjaro or Wegovy following a clinical assessment. These medications are typically used alongside reduced-calorie diets and increased physical activity. Eligibility depends on your BMI, health conditions, and individual circumstances. Our GLP-1 weight loss calculator can help you understand potential outcomes with medication.
Is BMI accurate for everyone in obese categories?
BMI is a useful screening tool but has limitations. It doesn't account for muscle mass, so very fit or muscular individuals may have high BMI without excess body fat. It also doesn't distinguish where fat is stored. Your GP can assess whether BMI alone is appropriate for you or whether additional measurements like waist circumference are needed.
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.