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 Weight and Why Does It Matter for Your Health?
Weight is the force exerted by your body due to gravity, measured in kilograms, stone, or pounds. In UK health context, your weight is one of several important health markers used alongside BMI, waist circumference, and overall fitness to assess wellbeing. The NHS uses weight measurements as part of routine health checks to screen for conditions like type 2 diabetes, heart disease, and high blood pressure. Understanding what your weight means — not just the number itself — is key to making informed health decisions. Weight is influenced by many factors including muscle mass, bone density, body composition, and hydration levels, which is why weight alone doesn't tell the complete health story.
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.
How UK Health Services Define and Use Weight
In NHS guidance and UK clinical practice, body weight refers to the total mass of your body measured in kilograms (kg), or converted to stone and pounds for patient-friendly communication. Weight is recorded at GP appointments and used to calculate your BMI (Body Mass Index) alongside your height to screen for overweight and obesity. Use our free BMI calculator above to check your personal BMI instantly. The NHS recognises that weight is affected by genetics, age, medications, medical conditions, hormonal changes, and lifestyle factors — it is not simply a measure of willpower or effort. Weight measurements are taken during routine health checks, pre-surgery assessments, and when monitoring chronic conditions. For adults, healthy weight ranges are defined by NHS BMI categories: healthy weight is a BMI of 18.5–24.9, with lower thresholds (18.5–22.9) recommended for people of South Asian, Chinese, Black African, or Black Caribbean heritage due to higher health risks at lower BMI levels.
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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.
Weight Management and UK Health Resources
If you're concerned about your weight or want to understand your personal healthy weight range, your GP is the best starting point for advice tailored to your individual circumstances. The NHS offers free weight management support through tier 1 and tier 2 services, including digital tools, community programmes, and behaviour change support. For weight loss, the NHS recommends a sustainable rate of 0.5–1 kg per week, achieved through a modest calorie deficit and increased physical activity. Convert your weight between kg, stone, and lbs instantly using our free weight converter on this page — understanding your weight in both metric and imperial measurements helps you track progress clearly. Track your weight loss journey with our free progress tracker if you're working towards a weight management goal. More intensive support, including prescription weight loss medications, is available through specialist tier 3 services following GP referral, though availability varies by region.
- 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 difference between weight and BMI?
Weight is the total mass of your body measured in kg, stone, or pounds. BMI combines your weight and height to estimate whether your weight is in a healthy range for your height. Two people with the same weight can have different BMIs if they differ in height. BMI is useful for screening but has limitations — it doesn't account for muscle mass or body composition.
Why does the NHS measure weight at GP appointments?
Weight is measured to screen for health conditions linked to excess weight, including type 2 diabetes, heart disease, and high blood pressure. Your weight, combined with other measurements like waist circumference, helps your GP assess your overall health risk and offer support if needed.
What is a healthy weight range for UK adults?
A healthy weight range is defined by BMI 18.5–24.9 according to NHS guidelines. For South Asian, Chinese, Black African, or Black Caribbean adults, the healthy range is BMI 18.5–22.9. Your personal healthy weight depends on your height, age, muscle mass, and overall health. Your GP can advise your individual targets.
Does weight include muscle and fat equally?
Weight includes everything — muscle, fat, bone, organs, and water. This is why two people of the same weight can look different and have different health profiles. This is why BMI has limitations and why body composition matters alongside weight.
How can I track my weight loss progress?
Record your weight regularly — weekly is typical — and look at trends over time rather than daily fluctuations. Use our free progress tracker on this page to log your weight and visualise your journey. Combine weight tracking with measurements like waist circumference and how clothes fit for a fuller picture of progress.
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.