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
Height, Age and Weight — What Matters for Your Health
Your height, age and weight all play a role in determining whether you're at a healthy weight, but they don't tell the full story on their own. In the UK, we use height and weight together to calculate BMI (Body Mass Index), which is the NHS standard screening tool for assessing healthy weight. Age also matters — healthy weight ranges and body composition change naturally as we get older. This guide explains how these three factors work together and what NHS guidance says about achieving and maintaining a healthy weight.
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 Height, Age and Weight Work Together for Health
Your height and weight are the two measurements used to calculate your BMI, which helps identify whether you're in a healthy weight range according to NHS guidelines. The healthy BMI range is 18.5 to 24.9 for most UK adults — though lower thresholds apply for people of South Asian, Chinese, Black African, or Black Caribbean heritage.
Age is also significant. Muscle mass naturally decreases with age (a process called sarcopenia), meaning you may need fewer calories to maintain the same weight as you age. Older adults also have different health considerations — waist circumference and body composition become increasingly important alongside BMI.
Use our free BMI calculator above to check your personal BMI based on your height and weight. This gives you an instant snapshot of where you fall on the NHS healthy weight scale. For a complete picture, you can also track how your weight changes over time using our free progress tracker, which helps you see patterns and trends in your weight management journey.
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.
NHS Guidance on Healthy Weight by Age
The NHS recommends a healthy weight for adults based on height and BMI, not age — meaning a healthy weight range applies to all adults regardless of age. However, how you achieve and maintain that weight varies by age group.
- Young adults (18–40): Focus on building healthy habits and maintaining stable weight through balanced diet and regular activity.
- Middle-aged adults (40–65): Monitor weight carefully as metabolic rate naturally slows; increased physical activity becomes more important.
- Older adults (65+): Balance is key — being slightly overweight (BMI 25–27) may be protective, but maintaining muscle through strength training matters more than the number on the scales.
Your GP can give personalised advice about what a healthy weight means for you, based on your age, medical history, and individual circumstances.
- 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's the healthy weight range for my height?
Use our free BMI calculator above — enter your height and weight to see your BMI and whether you're in the healthy range (18.5–24.9). The healthy weight range varies significantly by height. For example, a healthy weight for someone 5ft 8in is roughly 55–74kg (8st 10lbs–11st 9lbs). Your GP can discuss what's healthy specifically for you.
Does age affect how much you should weigh?
Age doesn't change the BMI healthy weight range itself (18.5–24.9 applies to all adults), but it does affect how you maintain weight. Metabolism naturally slows with age, muscle mass decreases, and older adults may benefit from more physical activity to maintain muscle. A healthcare professional can advise what's realistic and healthy for your age.
How do I convert my weight to check against UK guidelines?
Use our free weight converter to switch between kg, stone and pounds. UK NHS guidance uses kg, but many UK adults prefer stone and pounds. For example, 70kg equals 11 stone 0.1lbs. Once you have your weight in any unit, use the BMI calculator to see where you fit on NHS healthy weight guidelines.
Is BMI the only measure of healthy weight?
BMI is a useful NHS screening tool, but it has limitations — it doesn't distinguish between muscle and fat, and doesn't account for where fat is stored. Waist circumference is also important: men should aim for under 94cm, women under 80cm. Your GP can assess your overall health using multiple measures, not just BMI.
Should I lose weight if I'm overweight according to BMI?
The NHS recommends weight loss if your BMI is 25 or above (or lower thresholds for certain ethnic groups) alongside weight-related health conditions like high blood pressure or type 2 diabetes. Even losing 5–10% of your body weight can improve health. Always discuss weight management with your GP before making significant changes.
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.