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 Normal Body Weight by Age?
There's no single "normal" body weight that applies to everyone at a given age—it depends on your height, sex, muscle mass, and individual health. However, the NHS provides guidance on healthy weight ranges using BMI (Body Mass Index), which applies across all ages in adults. A healthy BMI is 18.5 to 24.9 for most adults, though thresholds are lower for people of South Asian, Chinese, Black African, or Black Caribbean heritage. Rather than focusing on age-specific numbers, the most useful approach is to check where your weight sits within the healthy BMI range for your height. You can use our free BMI calculator above to find your personal healthy weight range instantly, or try our weight converter to see your weight in different units (kg, stone, lbs).
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.
NHS Healthy Weight Ranges by Height
The NHS doesn't publish specific "normal" weights by age, but instead recommends using BMI as the main screening tool. A healthy BMI of 18.5–24.9 applies to all adults regardless of age. To find your healthy weight range, multiply 18.5 and 24.9 by your height in metres squared.
Example: If you're 1.70m tall (5ft 7in), your healthy weight range is approximately 53–71 kg (8st 5lbs–11st 2lbs).
- Underweight: BMI below 18.5 (may need medical review)
- Healthy weight: BMI 18.5–24.9
- Overweight: BMI 25–29.9
- Obese: BMI 30 or above
These categories apply the same way whether you're 20, 40, or 60 years old. However, age-related changes in muscle mass and metabolism mean weight management approaches may differ across life stages.
Clinically BackedWeight Loss
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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.
Age, Metabolism, and Weight Management
As we age, several physiological changes affect weight and body composition. Muscle mass naturally decreases by approximately 3–8% per decade from age 30 onwards, which lowers metabolic rate and makes maintaining a healthy weight more challenging. Hormonal changes—particularly in women approaching and during menopause—can also affect weight distribution and ease of weight loss.
Despite these changes, the healthy BMI range remains the same across all adult ages. If you're concerned about weight management as you age, your GP can provide personalised advice. For sustainable weight loss alongside lifestyle changes, prescription options like GLP-1 medications may be appropriate—your GP or a healthcare professional can assess eligibility based on your individual health context and whether you meet NHS criteria.
- 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 normal body weight change with age?
Not according to NHS guidance. The healthy BMI range (18.5–24.9) applies to all adults regardless of age. However, maintaining a healthy weight often becomes more challenging with age due to declining muscle mass and metabolic changes. Use our free BMI calculator to check your healthy weight range for your specific height.
What's the average weight for a UK adult?
According to ONS data, the average UK adult man weighs approximately 85.7 kg (13st 7lbs) and the average woman weighs approximately 71.6 kg (11st 3lbs). However, average weight is not the same as healthy weight—healthy weight depends on your individual height and BMI.
How do I know if my weight is normal for my height?
Calculate your BMI using your height and weight. A BMI of 18.5–24.9 is considered healthy for most UK adults. Our free BMI calculator above will show you your personal BMI and healthy weight range instantly, with NHS guidance included.
Do South Asian or Black African adults have different healthy weight ranges?
Yes. The NHS recommends lower BMI thresholds for people of South Asian, Chinese, Black African, and Black Caribbean heritage because these groups have higher health risks at lower BMI levels. Healthy BMI for these groups is 18.5–22.9 instead of 18.5–24.9.
Can I lose weight safely at any age?
Yes, but approach matters. The NHS recommends losing 0.5–1 kg per week for sustainable results at any age. Older adults should ensure adequate protein intake to preserve muscle during weight loss. If you're considering prescription weight loss support, speak to your GP about eligibility and whether options like GLP-1 medications are appropriate for you. ```
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.