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
How Do You Check Your BMI
Checking your BMI is simple and takes just two measurements: your weight and height. The NHS uses BMI as a screening tool to help assess whether your weight falls within a healthy range for your height. You can calculate your BMI manually using the standard bmi formula, or use our free BMI calculator above for gradual improvement. Understanding your BMI is the first step towards making informed decisions about your health, though it's important to know that BMI has limitations and doesn't account for muscle mass or where fat is stored on your body.
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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 BMI categories are based on your calculated BMI number and help classify your weight status. According to NHS guidance, a healthy BMI ranges from 18.5 to 24.9. A BMI below 18.5 is classified as underweight, whilst 25.0 to 29.9 is overweight, and 30.0 or above is obese.
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower bmi thresholds because these groups face higher health risks at the same BMI level. For these populations, a healthy BMI is 18.5 to 22.9, with overweight starting at 23.0.
The bmi range uk standard uses these categories consistently across NHS services. Your GP can explain what your individual BMI means for your health and whether any action is needed.
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 Support and Next Steps
If your BMI falls outside the healthy range, the NHS offers support through its structured weight management pathway. Your first step is usually to speak with your GP, who can assess your overall health, discuss any weight-related conditions, and potentially refer you to specialist services if appropriate.
The NHS recognises that weight management requires support, not judgment. Depending on your BMI and health circumstances, your GP might recommend lifestyle changes, community weight management programmes, or refer you to tier 3 specialist services. These services can discuss options including structured diet and exercise programmes, and in some cases, prescription weight loss medications. You can also track your progress using our free progress tracker to monitor changes over time.
- 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 BMI formula and how do I calculate it?
The BMI formula is: weight in kilograms ÷ (height in metres squared). For example, if you weigh 70kg and are 1.75 metres tall, your BMI would be 70 ÷ (1.75²) = 22.9. You can use our free BMI calculator above to calculate this instantly without a UK pharmacy maths.
What is considered a healthy BMI according to the NHS?
According to NHS guidance, a healthy BMI is between 18.5 and 24.9 for most adults. 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 due to higher health risks at standard BMI levels.
What should I do if my BMI is above the healthy range?
If your BMI is above the healthy range, speak with your GP. They can assess your individual health, discuss any weight-related conditions, and suggest appropriate support. This might include lifestyle changes, community programmes, or referral to specialist weight management services.
Why does the NHS use different BMI categories for certain ethnic groups?
Research shows that South Asian, Chinese, Black African, and Black Caribbean populations have increased risk of type 2 diabetes and cardiovascular disease at lower BMI levels compared to other groups. The NHS recommends lower thresholds for these populations to ensure timely health intervention.
What are the limitations of BMI as a health measure?
BMI doesn't distinguish between muscle and fat, so athletes may have high BMI despite low body fat. It also ignores where fat is stored on your body and doesn't account for age, bone density, or individual health factors. Use it as a screening tool alongside other measures like waist circumference and professional health assessment.
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.