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
Understanding Age, Height, Weight and Health
Age, height, and weight are three key factors that doctors use to assess your overall health and risk of weight-related conditions. Rather than looking at weight alone, NHS health professionals use these measurements together — typically through BMI calculations and waist circumference — to build a complete health picture. Your age matters because metabolic rate changes over time, height determines your healthy weight range, and weight itself reflects your current health status. Understanding how these three factors work together helps you make informed decisions about your health and whether you might benefit from lifestyle changes or professional support.
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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.
How Age, Height, and Weight Work Together
Your height determines your healthy weight range. The NHS uses height to calculate BMI — a screening tool that shows whether your weight is healthy for your frame size. A person who is 5ft 8in (173cm) tall has a different healthy weight range than someone who is 5ft 2in (160cm) tall, even if they have the same BMI number.
Your age affects metabolism and health risks. As you age, your metabolism naturally slows, muscle mass decreases, and the risks associated with excess weight may change. Older adults may develop weight-related health conditions like type 2 diabetes, heart disease, or joint problems more readily. Younger adults have more metabolic flexibility but should still aim for a healthy weight to prevent future complications.
Your weight reflects your current health status. Combined with height and age, your weight helps determine your BMI category — underweight, healthy weight, overweight, or obese — according to NHS guidelines. However, BMI has limitations: it doesn't distinguish between muscle and fat, and ethnicity can affect the healthy thresholds that apply to you.
- South Asian, Chinese, Black African, and Black Caribbean adults have different healthy BMI thresholds
- Regular weight monitoring helps track health trends over time
- Weight loss of just 5–10% can bring significant health benefits
Clinically BackedWeight Loss
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.
Finding Your Healthy Weight Range Using UK Health Guidance
Your healthy weight depends on your height, age, and individual health factors. Use the free BMI calculator on this page to find your current BMI category and healthy weight range instantly. For most UK adults, a healthy BMI is between 18.5 and 24.9 — though lower thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage.
If you're concerned about your weight, your GP can provide personalised advice based on your full health picture. They'll consider your age, any existing health conditions, family history, and lifestyle. If weight loss support is appropriate for you, NHS services range from digital tools and weight management programmes (Tier 1–2) to specialist services and prescription medications (Tier 3–4). Track your progress over time using our free progress tracker to stay motivated and identify patterns.
- 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 healthy weight for my height and age?
Your healthy weight range depends on your height and BMI category (ideally 18.5–24.9 for most UK adults). Use our free BMI calculator above by entering your height and weight — it will show your healthy range instantly. Age affects metabolism and health risk, but BMI thresholds remain the same across age groups. Your GP can provide personalised guidance.
How does age affect healthy weight?
As you age, metabolism slows and muscle mass naturally decreases, meaning you may need fewer calories to maintain weight. Older adults are at higher risk of weight-related diseases like type 2 diabetes and heart disease. However, maintaining a healthy weight throughout life reduces these risks. Regular physical activity helps preserve muscle as you age.
Why is height important for determining healthy weight?
Height determines your healthy weight range because weight is distributed across your frame size. Two people weighing the same may have very different BMIs if they have different heights. The NHS uses height to calculate BMI, which is why our free weight converter and BMI calculator ask for both measurements.
Can I use the same healthy weight scale for all ages?
BMI categories (healthy, overweight, obese) are the same for all adults over 18. However, your personal health needs and risk factors change with age. Children use different growth charts entirely. Always consult your GP for age-specific health advice.
What should I do if I'm outside the healthy weight range for my height?
If your BMI falls outside 18.5–24.9, speak to your GP. They can assess your individual health, discuss lifestyle changes like diet and exercise, and — if appropriate — refer you to NHS weight management services. Evidence shows that losing just 5–10% of body weight brings meaningful health benefits.
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.