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
Check Your BMI Using NHS Guidelines
Checking your BMI is a straightforward way to understand whether your weight falls within a healthy range according to NHS guidance. BMI (Body Mass Index) is calculated using your height and weight, and the NHS uses standardised BMI categories to help assess health risk. Whether you're concerned about your weight or simply want to monitor your health, knowing your personal BMI range is an important first step. Use our free BMI calculator above to check your BMI instantly, and read on to understand what your result means according to NHS recommendations.
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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 What They Mean
The NHS defines healthy weight using BMI ranges that apply to most UK adults. Your BMI is calculated by dividing your weight in kilograms by your height in metres squared. According to NHS guidance, the standard BMI categories are: underweight (below 18.5), healthy weight (18.5–24.9), overweight (25.0–29.9), obese Class I (30.0–34.9), obese Class II (35.0–39.9), and severely obese (40.0 and above).
However, the NHS also recognises that lower BMI thresholds apply to people of South Asian, Chinese, Black African, and Black Caribbean heritage. For these groups, a healthy weight is 18.5–22.9, overweight starts at 23.0, and obesity begins at 27.5. This is because these populations face higher cardiovascular and diabetes risk at lower BMI levels.
It's important to understand that BMI has limitations. It doesn't distinguish between muscle and fat, so athletes may have a high BMI despite low body fat. BMI also doesn't account for where fat is stored—waist circumference matters too. Despite these limitations, BMI remains a useful screening tool and is what the NHS uses in clinical practice.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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 your BMI falls outside the healthy range, the NHS offers a structured weight management pathway. Tier 1 involves self-help—using digital tools, community programmes, and the NHS Weight Loss Plan. Tier 2 adds primary care support from your GP, including behaviour change coaching and group programmes.
Tier 3 is specialist weight management, where you may be offered prescription medications like GLP-1 injections alongside intensive lifestyle support. Tier 4 covers bariatric surgery for severe obesity with significant health complications.
You should contact your GP if you're concerned about your weight, especially if you have weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. Your GP can assess your individual situation and refer you to the appropriate tier of support. Use our free BMI calculator to check your current BMI, and then discuss the result with your GP to plan next steps.
- 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 a healthy BMI according to the NHS?
According to NHS guidance, a healthy BMI for most UK adults is between 18.5 and 24.9. However, for people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends a lower healthy range of 18.5 to 22.9, as these groups have higher health risk at standard BMI thresholds.
How do I calculate my BMI?
BMI = weight (kg) ÷ height (m)². For example, if you weigh 70kg and are 1.73m tall, your BMI = 70 ÷ (1.73²) = 23.4. Use our free BMI calculator above to calculate yours instantly in seconds.
Does BMI tell me everything about my health?
No. BMI is a useful screening tool but has limitations. It doesn't distinguish between muscle and fat, so athletes may have a high BMI with low body fat. Waist circumference and overall fitness also matter. Your GP can provide personalised health advice beyond BMI alone.
What should I do if my BMI is outside the healthy range?
Contact your GP to discuss your weight and health. They can assess whether you need support and refer you to appropriate services. The NHS offers a structured pathway from self-help tools through to specialist weight management and, if needed, prescription medications.
Can ethnicity affect BMI recommendations?
Yes. The NHS recommends lower BMI thresholds for South Asian, Chinese, Black African, and Black Caribbean adults because these groups have higher cardiovascular and diabetes risk at standard BMI levels. If you belong to these groups, ask your GP about ethnicity-adjusted BMI recommendations.
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.