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's a Healthy Weight for Your Age?
Your healthy weight depends far more on your height and body composition than your age alone. In the UK, the NHS uses BMI (Body Mass Index) as the primary screening tool for all adults, regardless of age. A healthy BMI is between 18.5 and 24.9, which applies from late teens through to older adults. However, age does affect metabolism, muscle mass, and how your body manages weight — so we'll explore what that means for you, and how you can use our free BMI calculator and weight converter to find your personal healthy weight range.
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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.
NHS Guidance on Healthy Weight Across Age Groups
The NHS does not publish separate healthy weight charts by age — instead, it uses BMI categories that apply to all adults aged 18 and over. A healthy BMI of 18.5–24.9 is the same whether you're 25 or 65. This is because BMI adjusts for height, making it applicable across age ranges.
However, age does affect weight management:
- Younger adults (18–40): Higher metabolic rates and muscle mass. Weight gained is often easier to lose with diet and activity changes. Many maintain healthy weight without medication.
- Middle-aged adults (40–60): Metabolism slows by approximately 2–8% per decade. Muscle loss accelerates after 40. Weight management may require more deliberate dietary and physical activity changes.
- Older adults (60+): Continued muscle loss, lower metabolic rate, and changes in appetite regulation. Maintaining muscle mass becomes increasingly important. Being slightly above the "healthy" BMI range may sometimes protect against frailty (this is a nuance worth discussing with your GP).
For all ages, the key health marker is not just weight, but also waist circumference — excess fat around the middle carries higher health risk regardless of age or BMI.
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.
Using NHS Health Tools to Find Your Healthy Weight
The best way to discover what a healthy weight means for you personally is to use our free BMI calculator — it takes your height into account and shows you the healthy weight range for your specific measurements, regardless of your age.
You can also use our weight converter to switch between kg, stone, and pounds, making it easy to understand your weight in whichever unit you prefer. Your GP can provide personalised advice about your ideal weight target based on your medical history, any existing health conditions, and your individual circumstances. They may also refer you to NHS weight management services if appropriate — these are available through your local integrated care board and can include support from dietitians and behavioural health specialists.
- 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 your healthy weight change as you get older?
Your BMI healthy range (18.5–24.9) remains the same throughout adulthood according to NHS guidelines. However, the way your body manages weight changes — metabolism slows and muscle mass naturally decreases with age. This means maintaining a healthy weight may require more intentional dietary and activity choices in middle age and beyond. Your GP can advise on age-appropriate weight management strategies.
What's the average weight for UK adults by age?
UK average weights vary by age and sex, but data shows adults gradually gain weight through their 40s and 50s. According to Office for National Statistics (ONS) data, the average UK adult man weighs approximately 85.7kg (13st 7lbs) and the average adult woman approximately 71.6kg (11st 3lbs). However, "average" does not mean "healthy" — your healthy weight range depends on your height and BMI, not on how much others weigh.
Should older adults aim for a lower BMI than younger adults?
No — NHS guidance uses the same BMI categories (18.5–24.9 healthy range) for all adults regardless of age. However, for very elderly adults (75+) or those with frailty, some evidence suggests slightly higher BMI may be protective. Always consult your GP about your personal healthy weight target, as they can consider your individual health picture and any age-related factors specific to you.
How does age affect weight loss with diet and exercise?
Weight loss typically becomes slower with age due to declining metabolism and muscle mass loss. Younger adults may lose weight more quickly with the same calorie deficit, while older adults may need more time or greater dietary changes to achieve the same loss. This is normal. Including strength-building exercise becomes increasingly important with age to preserve muscle during weight loss. Your GP or a registered dietitian can advise on age-appropriate weight loss approaches.
Can I use the same healthy weight range if I'm over 60?
Yes — the NHS BMI healthy weight range (18.5–24.9) applies to all adults, including those over 60. Use our free BMI calculator to find your specific healthy weight range based on your height. However, older adults should always discuss their personal weight management goals with their GP, as factors like existing health conditions, medications, and muscle mass may mean your GP advises a slightly different target than the standard BMI range.
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.