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 a Healthy Weight According to Age?
There is no single "ideal" weight based on age alone — healthy weight depends primarily on height and individual body composition. The NHS uses BMI (body mass index) as the main screening tool for healthy weight across all adults, regardless of age. However, body composition, muscle mass, and where fat is stored also matter. Our free BMI calculator and weight converter help you understand what a healthy weight means for your specific height, and age-related health considerations can affect weight management strategies.
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 Age Affects Healthy Weight and Health Risk
Age influences how weight affects health risk, even at the same BMI. Younger adults (18–40) with a BMI under 25 generally face lower cardiovascular and metabolic disease risk. Middle-aged adults (40–65) may develop weight-related conditions like type 2 diabetes or high blood pressure more readily — NHS guidance suggests maintaining a BMI of 18.5–24.9 is particularly important during this period. Older adults (65+) face different considerations: whilst a slightly higher BMI (up to 27) may offer some protective benefits, central obesity (excess weight around the stomach) remains a significant risk factor. Age-related muscle loss (sarcopenia) also means that two people of the same BMI and height may have very different body compositions. This is why personalised health advice from your GP is essential — age, fitness level, and existing health conditions all matter beyond just height and weight.
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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 BMI Categories and Age-Specific Context
The NHS BMI categories remain the same across all adult ages:
- Healthy weight: BMI 18.5–24.9
- Overweight: BMI 25.0–29.9
- Obese: BMI 30.0 and above
However, age affects how aggressively health conditions develop at each BMI level. Younger adults often have time to address weight through lifestyle changes, whilst older adults may benefit from earlier intervention if overweight. Ethnicity also matters — adults of South Asian, Chinese, Black African, or Black Caribbean heritage have lower recommended BMI thresholds, with a healthy range of 18.5–22.9. Use our free BMI calculator above to find your personal BMI and healthy weight range for your height, then discuss age-specific health strategies with your GP.
- 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 healthy weight change as you get older?
Healthy BMI ranges remain consistent (18.5–24.9), but age affects how quickly weight-related diseases develop and how your body responds to weight changes. Older adults may need earlier intervention for weight management. Genetics, fitness level, and medical history also influence healthy weight at any age.
What is the average UK weight by age group?
Average weights vary widely by age, gender, and height. UK adult men average around 85.7kg (13st 7lbs) and women average 71.6kg (11st 3lbs). However, average is not the same as healthy — use your height and BMI to find your healthy weight range rather than comparing to averages.
Can I use the same BMI calculator at different ages?
Yes — BMI calculation method remains identical across all adult ages (weight in kg ÷ height in metres squared). However, interpretation may differ slightly based on age-related health risk. Our free BMI calculator shows you your BMI and healthy range instantly.
Why do older adults sometimes have higher healthy weight ranges?
They don't — NHS BMI categories are identical. However, older adults with existing muscle loss may need gentler approaches to weight management. Some research suggests slightly higher BMI may offer protective benefits in very elderly people, but this is individualised. Always discuss with your GP.
How do I find my healthy weight range?
Calculate your BMI using your height and current weight with our free BMI calculator above. Your healthy weight range is any weight that gives you a BMI of 18.5–24.9 (or 18.5–22.9 if you're of South Asian, Chinese, Black African, or Black Caribbean heritage). Use our weight converter to switch between kg and stone instantly.
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.