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 to Check Your BMI Using NHS Guidelines
Checking your BMI (Body Mass Index) is a simple way to understand whether your weight falls within a healthy range according to NHS standards. BMI is calculated using your height and weight, and the NHS has specific categories and thresholds for UK adults. Use our free BMI calculator above to check your personal BMI instantly, then compare your result against the official NHS ranges to see what it means for your health.
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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 Healthy Ranges
The NHS BMI formula is straightforward: divide your weight in kilograms by your height in metres squared. The healthy BMI range according to NHS guidelines is 18.5 to 24.9 for most UK adults. Here are the official BMI categories UK uses:
- 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)
If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds — with a healthy range of 18.5 to 22.9. Even a small increase in overweight BMI threshold can significantly affect your health risk in these populations.
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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.
Important BMI Limitations and What Else Matters
BMI limitations are important to understand. BMI does not distinguish between muscle and fat — athletes and very muscular individuals may have a high BMI but low body fat. It also doesn't account for where fat is stored; abdominal fat poses greater health risks than fat stored elsewhere. Use our free weight converter to compare your weight across units (kg, stone, pounds), then discuss your BMI result with your GP. Your GP can provide personalised health advice and may recommend measuring your waist circumference alongside BMI, as this is a better indicator of cardiovascular risk.
- 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's the difference between NHS BMI categories and other BMI charts?
The NHS uses evidence-based thresholds aligned with UK health data and clinical guidelines. Other charts may use different categories or thresholds. Always refer to NHS guidelines for UK health recommendations, and discuss your personal BMI with your GP for tailored advice.
Can I check my BMI if I'm pregnant?
BMI is less accurate during pregnancy because weight gain is expected and necessary. Your GP or midwife will monitor your health differently during pregnancy using other measures. Always discuss weight concerns with your healthcare team.
What should I do if my BMI falls outside the healthy range?
A BMI outside the healthy range doesn't mean you need to panic, but it's worth discussing with your GP. They can assess your individual health, recommend lifestyle changes if appropriate, and refer you to specialist services if needed. Small changes often make a meaningful difference.
Is BMI the only measure of health I should check?
No. BMI is a useful screening tool but doesn't tell the whole story. Your GP will also consider your waist circumference, blood pressure, cholesterol, fitness level, and personal health history. Use our BMI calculator alongside these other measures.
Do ethnic background and age affect my healthy BMI range?
Yes. The NHS recognises that South Asian, Chinese, Black African, and Black Caribbean populations have higher health risks at lower BMI levels, so lower thresholds apply. Age also matters — elderly adults may have different healthy ranges. Your GP can advise on ranges specific to you.
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.