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
What Is BMI Health and What Does It Mean?
Your BMI (body mass index) is a measure of your body weight in relation to your height, and it's one of the main tools the NHS uses to assess whether your weight falls within a healthy range. Understanding your BMI health status can help you identify potential health risks and take steps towards better wellbeing. BMI is calculated by dividing your weight in kilograms by your height in metres squared. Whilst it's useful as a screening tool, BMI is just one part of the overall health picture. Use our free BMI calculator above to check your personal BMI instantly and see which category you fall into.
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.
BMI Range UK and Health Categories
The NHS provides clear BMI categories to help you understand what your BMI number means for your health. Your BMI range UK is classified as follows:
- Underweight: Below 18.5 — may indicate nutritional concerns
- Healthy weight: 18.5 to 24.9 — associated with lower health risks
- Overweight: 25.0 to 29.9 — increased risk of certain health conditions
- Obese (Class I): 30.0 to 34.9 — significantly increased health risks
- Obese (Class II): 35.0 to 39.9 — very high health risks
- Severely obese (Class III): 40.0 and above — serious health concerns
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds due to higher cardiovascular and metabolic disease risk at the same BMI levels. A healthy BMI for these groups is 18.5 to 22.9. The overweight BMI threshold for these populations starts at 23.0. Understanding your specific healthy BMI range helps you set realistic health goals and work with your GP on appropriate interventions.
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.
BMI Limitations and Complementary Health Measures
Whilst BMI is useful, the BMI formula has important limitations. It does not distinguish between muscle and fat — athletes and very muscular individuals may have a high BMI but low body fat. BMI also does not account for where fat is stored, and excess weight around the stomach carries greater health risks than weight distributed elsewhere. Additionally, BMI may be less accurate for older adults who have experienced natural muscle loss, or during pregnancy.
For a fuller health picture, consider your waist circumference alongside your BMI. The NHS recommends that men keep their waist below 94cm (37 inches) and women below 80cm (31.5 inches) for optimal health. You can also convert your weight using our free weight converter to understand your weight in different units, which may help you track progress more effectively.
- 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 NHS guidelines, a healthy BMI is between 18.5 and 24.9 for most adults. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, a healthy BMI is 18.5 to 22.9. Your GP can advise on what target BMI is appropriate for your individual health situation.
How do I calculate my BMI?
The BMI formula is: weight (kg) ÷ height (m)². For example, if you weigh 70kg and are 1.75m tall, your BMI would be 70 ÷ (1.75)² = 22.9. Use our free BMI calculator above for an instant calculation.
What BMI is classed as overweight?
A BMI of 25.0 to 29.9 is classified as overweight according to NHS categories. This range indicates increased health risk compared to healthy weight, though many people in this range have no health problems. Your GP can discuss personalised health advice.
What does a high BMI mean for my health?
A higher BMI is associated with increased risk of type 2 diabetes, heart disease, high blood pressure, certain cancers, and joint problems. However, BMI is just one indicator — overall health depends on fitness, diet, family history, and lifestyle. Your GP can provide personalised health assessment.
Are there limitations to BMI?
Yes. BMI does not account for muscle mass, so athletes may have high BMI but good health. It ignores where fat is stored and is less accurate for elderly people and during pregnancy. Combining BMI with waist measurement gives a better health picture than BMI alone.
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.