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 straightforward — it's a simple calculation based on your weight and height. Your BMI (body mass index) is a useful screening tool that helps assess whether you're at a healthy weight according to NHS guidelines. You can calculate it manually using the BMI formula, or use our free BMI calculator above to get your result instantly. Understanding your BMI range is the first step towards making informed health decisions about your weight.
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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.
The BMI Formula and How to Calculate It
BMI is calculated using a simple BMI formula that divides your weight by your height squared. In metric units (used by the NHS), the calculation is: BMI = weight in kg ÷ height in metres². For example, if you weigh 70kg and are 1.75 metres tall, your BMI would be 70 ÷ (1.75 × 1.75) = 22.9. Once you have your number, you can check it against the NHS BMI categories:
- Below 18.5 = Underweight
- 18.5–24.9 = Healthy weight
- 25.0–29.9 = Overweight
- 30.0–34.9 = Obese (Class I)
- 35.0–39.9 = Obese (Class II)
- 40.0+ = Severely obese (Class III)
Use our BMI calculator on this page to skip the maths — enter your weight and height, and your healthy BMI result appears instantly with your NHS category.
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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 What Else Matters
While BMI is useful, it has important limitations. BMI does not distinguish between muscle and fat — athletes may have a high BMI but low body fat. It also doesn't account for where fat is stored; waist measurement is equally important. For this reason, the NHS recommends using BMI alongside waist circumference as part of a complete health picture. Men with a waist over 94cm (37in) and women over 80cm (31.5in) have increased health risks, regardless of BMI. Your GP can provide personalised advice about what your BMI means for your individual health, especially if you have other health conditions.
- 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.
Can I check my BMI with weight in stone and pounds?
Yes. Convert your weight to kilograms first — use our free weight converter on this page. For example, 11 stone (154lbs) converts to approximately 70kg. Then use the BMI formula or our calculator. The NHS uses kg for clinical measurements, so converting ensures accuracy.
What's the difference between healthy BMI ranges for different ethnicities?
The NHS recommends lower BMI thresholds for people of South Asian, Chinese, Black African, and Black Caribbean heritage. Their healthy BMI range is 18.5–22.9 (versus 18.5–24.9 for other groups) because these populations face higher cardiovascular and diabetes risk at lower BMI levels.
Is BMI accurate for pregnant women or elderly people?
BMI is less accurate during pregnancy and in elderly adults. During pregnancy, BMI changes naturally and doesn't reflect body composition accurately. In older adults, muscle loss with age means BMI may overestimate health risks. Your GP can assess your health more comprehensively.
What BMI count is considered overweight?
According to NHS guidelines, an overweight BMI threshold starts at 25.0. A BMI between 25.0–29.9 is classified as overweight. Above 30 moves into the obese category. Even modest weight loss (5–10% of body weight) can have significant health benefits.
Should I use my BMI to set a weight loss goal?
Yes — use your BMI to identify a healthy weight range for your height, then set realistic targets. For example, at 1.75m, a healthy BMI (18.5–24.9) corresponds to approximately 56–76kg. Our BMI calculator shows your healthy range instantly. Combine this with our progress tracker to monitor your journey. ```
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.