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
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BMI Using Waist Measurement: NHS Health Assessment
While BMI is useful, the NHS recommends checking your waist measurement too, as it better reflects where fat is stored on your body. A larger waist circumference indicates increased health risks independent of your BMI, particularly for cardiovascular disease and type 2 diabetes. The NHS combines both measurements for a more complete health picture. This guide explains NHS waist thresholds, how to measure correctly, and why waist circumference matters alongside the standard BMI formula. Use our free BMI calculator above to check your BMI, then measure your waist to get a full health assessment.
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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 Waist Circumference and BMI Thresholds
The NHS recommends checking both BMI and waist circumference for a complete health risk assessment. Waist measurement is particularly important because it indicates abdominal fat, which poses greater health risks than fat stored elsewhere on your body.
NHS waist circumference thresholds for adults:
- Men: over 94cm (37 inches) = increased risk; over 102cm (40 inches) = high risk
- Women: over 80cm (31.5 inches) = increased risk; over 88cm (34.5 inches) = high risk
These thresholds apply regardless of your BMI range. Someone with a healthy BMI but a large waist circumference still has elevated health risks. For South Asian, Chinese, Black African, and Black Caribbean adults, lower waist thresholds apply: men over 90cm and women over 80cm indicate increased risk. The NHS weight management pathway now routinely measures both metrics to provide personalised guidance.
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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.
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Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Why Waist Measurement Matters Alongside BMI
BMI has significant limitations—it doesn't distinguish between muscle and fat, and doesn't show where fat is stored. Waist circumference reveals abdominal fat accumulation, which is linked to insulin resistance, inflammation, and cardiovascular disease even at healthy BMI levels.
The NHS emphasises that a healthy waist measurement combined with a healthy BMI offers the best health outcome. If your waist exceeds NHS thresholds, your GP may recommend lifestyle changes, dietary adjustments, or—if you meet other criteria—prescription weight management options. Measuring your waist regularly alongside tracking your BMI using our BMI calculator helps you monitor progress and spot early warning signs. This dual-measurement approach is now standard across NHS weight management services.
- 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.
How do I measure my waist correctly for NHS assessment?
Stand upright without tensing your abdominal muscles. Place a measuring tape around your middle, at the level of your navel, keeping it horizontal. Breathe out normally and read the measurement. Take the measurement in centimetres for NHS comparison. Measure at the same time of day for consistency, ideally in the morning before eating.
Can I have a healthy BMI but still be at risk according to waist measurement?
Yes. The NHS recognises this is possible. A healthy BMI (18.5–24.9) combined with a waist exceeding NHS thresholds suggests excess abdominal fat, which increases cardiovascular and diabetes risk. This is why the NHS recommends assessing both measurements together rather than BMI alone.
What should I do if my waist circumference exceeds NHS thresholds?
Speak to your GP. They can assess your overall health risk and recommend personalised interventions. This might include lifestyle changes, dietary support, increased physical activity, or referral to NHS weight management services. Your GP may also check other risk factors like blood pressure and cholesterol.
Do waist thresholds differ for different ethnic backgrounds?
Yes. The NHS recommends lower waist thresholds for South Asian, Chinese, Black African, and Black Caribbean adults due to higher cardiovascular and diabetes risk at lower BMI levels. Men of these backgrounds should target under 90cm; women under 80cm for increased risk category.
How often should I measure my waist alongside my BMI?
Monthly measurements are reasonable for tracking progress. Use our free BMI calculator alongside your waist measurement to monitor both metrics together. Track changes over time with our progress tracker to identify trends and share results with your GP during health checks.
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.