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 High BMI — NHS Guidance for UK Adults
A high BMI (body mass index) indicates excess body weight relative to height, which can affect your health. The NHS classifies a BMI of 25 or above as overweight or obese, with specific thresholds varying by ethnicity. Understanding your BMI range and what it means for your health is an important first step in managing your wellbeing. Use our free BMI calculator above to check your personal BMI instantly and see where you fall within NHS categories.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 What They Mean
The NHS uses standardised BMI categories to assess weight-related health risk. These are calculated using the BMI formula: weight in kilograms divided by height in metres squared. According to NHS guidance, the BMI range for different categories is:
- Healthy weight: BMI 18.5 to 24.9
- Overweight: BMI 25.0 to 29.9
- Obese (Class I): BMI 30.0 to 34.9
- Obese (Class II): BMI 35.0 to 39.9
- Severely obese (Class III): BMI 40.0 and above
For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds due to higher cardiovascular risk at the same BMI. For these groups, a healthy BMI is 18.5 to 22.9, and overweight begins at 23.0. Understanding your BMI categories UK helps your GP assess your individual health risk.
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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 Pathway and When to Seek Help
If you have a high BMI, the NHS offers a structured weight management pathway starting with your GP. Tier 1 support includes self-help tools and digital programmes like the NHS Weight Loss Plan. Tier 2 involves community programmes and behaviour change interventions. Tier 3 services are specialist multidisciplinary weight management teams where prescription medications may be offered. Tier 4 covers bariatric surgery for severe obesity with significant health complications. Your GP can assess your individual situation, discuss BMI limitations (noting that BMI doesn't account for muscle mass), and refer you to appropriate support. Even a 5–10% reduction in body weight can significantly improve health outcomes including blood pressure, blood sugar control, and cardiovascular health.
- 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 counts as "high" according to the NHS?
The NHS classifies BMI of 25–29.9 as overweight, and 30 or above as obese. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the thresholds are lower — overweight begins at BMI 23 and obesity at 27.5. These adjusted thresholds reflect higher health risks in these populations at lower BMI levels.
Why does the NHS use different BMI thresholds for different ethnic groups?
Research shows that people from South Asian, Chinese, Black African, and Black Caribbean backgrounds face higher risks of type 2 diabetes and heart disease at lower BMI levels than the general population. The NHS recommends lower thresholds for these groups to ensure earlier intervention and better health protection.
What are the main limitations of BMI?
BMI doesn't distinguish between muscle and fat — athletes may have a high BMI but low body fat. It also ignores where fat is stored (waist circumference matters), and is less accurate for older adults, pregnant women, and certain medical conditions. Your GP can discuss these BMI limitations and recommend additional health assessments.
Can I use a BMI calculator to assess my health risk?
Yes, our free BMI calculator on this page gives you an gradual improvement and shows where you fall within NHS categories. However, BMI is a screening tool only. For personalised health advice, especially if you have a high BMI, consult your GP who can assess your complete health picture including blood pressure, cholesterol, and family history.
What should I do if my BMI is high?
Contact your GP for an assessment. They can discuss your individual health risks, check for weight-related conditions like type 2 diabetes, and refer you to NHS weight management services if appropriate. The NHS pathway includes support at every tier — from self-help digital tools to specialist services and medications — so there's support available for everyone.
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.