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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How to Measure Weight Accurately — UK Health Guidance
Measuring your weight is a simple first step in understanding your health, but doing it correctly matters. In the UK, most adults measure weight in stone and pounds, though the NHS uses kilograms for clinical records. Knowing how to measure weight accurately — and understanding what your weight means for your health — helps you track progress effectively and make informed decisions about weight management. This guide covers UK best practices for weighing yourself and how your measurements relate to healthy weight thresholds recommended by the NHS.
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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.
Best Practices for Accurate Weight Measurement
For accurate and consistent weight measurements, follow these NHS-supported guidelines:
- Weigh yourself at the same time each day — morning is ideal, after using the toilet but before eating or drinking. This minimises daily fluctuations from food and water retention.
- Use the same scales consistently — different scales may show different readings. Digital scales are more reliable than mechanical ones.
- Wear similar clothing — weigh yourself in minimal clothing or the same outfit each time to avoid clothing weight affecting your reading.
- Check scale calibration — ensure your scales are on a hard, level surface, not carpet. Digital scales should be recalibrated occasionally.
- Weigh weekly, not daily — the NHS recommends weekly weigh-ins rather than daily. Weight naturally fluctuates by up to 2kg daily due to water, food, and hormonal factors. Weekly measurements provide a clearer picture of actual progress.
Once you have your weight measurement, you can convert between UK measurements (stone and pounds) and metric (kilograms) using our free weight converter above, and calculate your BMI using our BMI calculator to understand where you fall on the NHS healthy weight scale.
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Understanding Weight in UK Health Context
Your measured weight is just one piece of your health picture. The NHS uses weight alongside height to calculate BMI (Body Mass Index), which indicates whether you fall into the underweight, healthy weight, overweight, or obese range. For UK adults, a healthy BMI is 18.5 to 24.9. However, BMI has limitations — it does not distinguish between muscle and fat, and ethnicity affects risk at the same BMI. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds.
Waist measurement is equally important. The NHS recommends measuring waist circumference: over 94cm (37 inches) for men or 80cm (31.5 inches) for women indicates increased health risk. Combined with weight measurement, waist circumference gives a more complete picture of your health risk profile than weight alone.
If you are concerned about your weight or health, speak with your GP, who can discuss your individual situation and advise on weight management strategies suited to you.
- 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 most accurate time to weigh myself?
Early morning is ideal — after using the toilet but before eating, drinking, or exercising. This minimises daily fluctuations from food, water, and hormones. Weigh yourself at the same time each morning for consistency and reliable progress tracking.
Why does my weight fluctuate by several kilograms day-to-day?
Daily weight changes are normal and usually not fat loss or gain. Fluctuations come from water retention, food in your digestive system, hormonal cycles, and even exercise-related inflammation. This is why the NHS recommends weekly weigh-ins rather than daily checks — weekly patterns are more meaningful than daily variation.
How do I convert my weight from stone to kilograms?
Use our free weight converter above, which instantly converts between stone, pounds, and kilograms. Alternatively, divide your weight in kilograms by 6.35 to get stone. For example, 70kg ÷ 6.35 = 11 stone. The weight converter also shows your BMI once you input your height.
Is weight the only thing I should measure for health?
No. The NHS emphasises measuring both weight and waist circumference. A high waist measurement indicates visceral fat around organs, which is a stronger predictor of health risk than BMI alone. Your GP can advise whether weight loss is needed based on your full health picture, not just the number on the scales.
How often should I weigh myself?
The NHS recommends weekly weigh-ins — typically once per week on the same day. This frequency captures true progress without the noise of daily fluctuations. If tracking weight loss or managing a health condition, keep a simple record over weeks and months. Our free progress tracker can help you log and visualise changes over time.
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.