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 Is Weight Calculated in the UK?
Weight is a fundamental health measurement, but understanding how it's calculated and what it means is essential for UK health contexts. Your weight is simply the total mass of your body, measured in kilograms, stone, or pounds. However, the way your weight is interpreted — and how it relates to your overall health — involves more than just a single number. In the UK, your weight is typically used alongside other measurements like height and waist circumference to assess health risk and guide healthcare decisions through NHS health guidance.
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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.
Understanding Weight Measurement in UK Healthcare
Weight measurement basics: Your weight is the gravitational force acting on your body mass, measured in kilograms (kg) in clinical settings or stone and pounds in everyday UK contexts. One stone equals exactly 14 pounds, or approximately 6.35 kg. The NHS uses metric measurements (kilograms) for clinical accuracy, though many UK adults find stone more familiar for personal weight tracking.
- Clinical settings: Weight measured in kg using calibrated scales
- Personal use: Often expressed in stone and pounds (e.g., 11 stone 7 pounds)
- Conversion: Use our free weight converter to switch between kg, stone, and lbs instantly
Weight alone doesn't tell the full health story. Your weight is combined with your height to calculate BMI (body mass index), which is the standard NHS screening tool for assessing whether your weight falls into a healthy range. For South Asian, Chinese, Black African, or Black Caribbean adults, the NHS recommends lower BMI thresholds because these groups face higher health risks at lower weights. Always remember that weight can fluctuate daily due to hydration, food intake, hormonal changes, and time of day — morning weight is typically lower than evening weight.
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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.
How Your Weight Is Used in UK Health Management
In UK healthcare, your weight is measured at GP appointments and used to calculate your BMI — a screening tool that helps identify whether you're in a healthy weight range. A healthy BMI falls between 18.5 and 24.9 according to NHS guidelines. Calculate your personal BMI using our free BMI calculator above to see where you fall on the NHS health scale.
Weight management context: If your weight indicates you're overweight or obese, your GP may discuss weight management options. This might include lifestyle changes (diet and exercise), referral to NHS tier 3 specialist weight management services, or — for eligible adults — prescription weight loss medication as part of a comprehensive health approach. Weight management combines your current weight measurement with your personal health history, comorbidities, and individual goals.
Track your weight progress over time using our free progress tracker, which helps you monitor changes and identify patterns. Sustainable weight loss is typically around 0.5–1 kg per week, and consistent tracking supports accountability. Your GP can provide personalized UK health advice about what your weight means for your individual health profile and what steps might be appropriate for 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 difference between weight measured in kg and stone?
One stone equals exactly 14 pounds or approximately 6.35 kg. The NHS uses kilograms for clinical measurements, but many UK adults find stone more intuitive for personal weight tracking. Our free weight converter lets you switch between kg, stone, and pounds instantly.
How does weight relate to BMI in UK health guidance?
Weight alone doesn't determine health risk. Your weight combined with your height calculates your BMI, which the NHS uses as a screening tool. A healthy BMI is 18.5–24.9, though lower thresholds apply for certain ethnic groups. Use our free BMI calculator to check your personal BMI instantly.
Why does my weight fluctuate day to day?
Daily weight changes are normal and due to hydration levels, food intake, hormones, and time of day. Morning weight is typically lower than evening weight. For accurate health tracking, weigh yourself at the same time each day, preferably in the morning before eating. Track trends over weeks, not individual daily changes.
What should I do if my weight falls outside the NHS healthy range?
If your weight indicates overweight or obesity, speak to your GP. They can assess your individual health, discuss lifestyle changes, refer you to specialist weight management services, or explore prescription options if eligible. Weight management is personalized based on your health history and goals.
How is weight used to determine eligibility for weight management medication?
Prescription weight loss medications like Mounjaro and Wegovy are prescribed based on BMI thresholds combined with health conditions. Generally, adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions, may be eligible. Your GP or prescriber will assess your individual circumstances and eligibility.
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.