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 Age, Height and Weight Affect Your Health
Your age, height, and weight work together to determine your overall health risk and healthy weight range. The NHS uses these three measurements to calculate BMI and assess whether your current weight falls within a healthy range for your body type. Age also matters — metabolism naturally slows as you get older, which can affect weight management. This guide explains how these factors connect and helps you understand what healthy weight means for you in the UK context.
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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 These Measurements Work Together
Height is the foundation of a healthy weight range. Two people weighing the same amount can have very different health risks depending on their height — this is why BMI uses height as a key variable. Weight alone is meaningless for health assessment; it must be considered relative to your height.
Age affects metabolism, muscle mass, and bone density. As you age, your basal metabolic rate typically decreases by about 2–8% per decade after age 30, meaning you burn fewer calories at rest. This is why older adults often need fewer calories to maintain the same weight, and why weight management may require different approaches at different life stages.
Use our free BMI calculator above to see how your height and weight combine to give your personal BMI — then compare it against NHS healthy weight ranges for your age group.
- Healthy BMI for most adults: 18.5 to 24.9
- For South Asian, Chinese, Black African, and Black Caribbean adults: 18.5 to 22.9
- Age does not change BMI categories, but it may influence weight management strategy
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.
Healthy Weight Ranges by Height
Your healthy weight range depends almost entirely on your height. A person who is 5ft 4in (163cm) will have a much lower healthy weight range than someone who is 6ft 2in (188cm). Use our weight converter to see your weight in different units (kg, stone, and lbs), then compare it to the healthy range for your height using our BMI calculator.
Key point: There is no "ideal" weight — only a healthy range based on BMI. Two people of the same height and weight might need different approaches to health depending on their age, muscle mass, fitness level, and existing health conditions. Your GP can provide personalised advice about what weight is healthy for you specifically.
- Height determines the range; weight determines where you fall within it
- Muscle weighs more than fat, so two people with the same BMI can look different
- Age influences how easily weight changes, not the healthy range itself
- 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.
Does age affect what a healthy weight should be?
No — healthy BMI categories are the same at every age. However, age affects metabolism and how your body composition changes. Older adults may find weight management more challenging because muscle mass naturally decreases with age. Your GP can advise on weight management strategies appropriate for your age and health status.
How do I work out my healthy weight range for my height?
Calculate your BMI using your height and weight. A BMI between 18.5 and 24.9 is healthy for most UK adults (18.5–22.9 for South Asian, Chinese, Black African, or Caribbean adults). Use the BMI calculator on this page, or ask your GP to calculate it for you. Your GP can also consider your individual health picture.
Can two people of the same height and weight have different body compositions?
Yes, absolutely. Weight alone does not tell you about muscle versus fat. Someone who exercises regularly may weigh the same as someone sedentary but have a much lower body fat percentage. BMI is a screening tool — it does not distinguish between muscle and fat, which is why your GP may ask about fitness and waist measurement too.
Why does metabolism slow with age?
As you age, you naturally lose muscle mass (sarcopenia) and your cells become less metabolically active. This means your body burns fewer calories at rest. From age 30 onwards, metabolic rate typically falls by about 2–8% per decade. This is why older adults often need fewer calories to maintain weight, and why weight management approaches may need to adjust over time.
Should I aim for a specific weight, or a weight range?
Aim for a healthy range, not a specific number. Your healthy weight range is typically quite wide — for example, someone who is 5ft 8in might have a healthy range of roughly 55–75kg (8st 10lbs to 11st 10lbs). Within this range, you can feel healthy and energetic. Your GP can advise on the best approach for your individual circumstances.
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.