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 at Your Age?
Weight recommendations vary more by height and overall health than by age alone. However, age does affect metabolism, muscle mass, and how your body responds to weight changes. This guide explains what NHS health guidance says about healthy weight across different ages, and how to assess whether your current weight is right for you using evidence-based tools and measurements.
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 Weight Changes with Age
As we age, several physiological changes affect weight and body composition. From our 30s onwards, we naturally lose approximately 0.5% of muscle mass each year — a process called sarcopenia. Muscle burns more calories than fat, so this gradual muscle loss slows metabolism and makes weight maintenance harder without intentional activity or dietary adjustments.
- Teenagers and young adults (13–25): Growth and hormonal development influence weight. BMI categories are the same as adults, but growth charts are used for under-18s.
- Adults (25–65): Weight tends to increase gradually due to reduced activity and metabolic changes. This is the key period for establishing healthy habits.
- Older adults (65+): Unintended weight loss becomes a health concern. Maintaining muscle mass is critical for strength, balance, and independence.
The best way to assess your healthy weight range at any age is using your height, not age — our free BMI calculator above gives you a personalised healthy weight range instantly.
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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 Healthy Weight Guidance Across Ages
The NHS defines healthy weight using BMI — a measurement based on your height and weight, not your age. A healthy BMI is 18.5 to 24.9 for all adults, regardless of age. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends a lower threshold of 18.5 to 22.9 due to increased health risks at lower BMI levels.
Weight management becomes increasingly important as we age because excess weight compounds health risks. Losing even 5% of body weight can meaningfully improve blood pressure, blood sugar, and cholesterol at any age. If you're concerned about your weight at your age, consult your GP — they can assess your individual health context and recommend appropriate next steps, which may include referral to weight management services.
- 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 age affect your healthy weight?
Your healthy weight is determined by your height, not your age. The NHS uses BMI (Body Mass Index) to define healthy weight ranges, which are the same for all adults. However, age does affect metabolism and muscle mass, making weight maintenance more challenging as you get older. Your GP can discuss your individual health needs at any age.
What's the average weight for adults in the UK?
According to NHS data, the average UK adult man weighs approximately 85.7 kg (13 stone 7 lbs) and the average adult woman weighs approximately 71.6 kg (11 stone 3 lbs). However, average weight is not the same as healthy weight — individual healthy weight depends on your height and overall health.
Is it harder to lose weight as you get older?
Yes — metabolism naturally slows with age due to reduced muscle mass and hormonal changes. Weight loss requires the same calorie deficit at any age, but maintaining that deficit can be more challenging. Resistance exercise helps preserve muscle and maintain metabolism. Weight management services can provide age-appropriate support.
What's a healthy weight range for someone who is 5ft 8in?
At 5ft 8in (173 cm), the healthy BMI range is approximately 55 kg to 74 kg (8 stone 8 lbs to 11 stone 8 lbs). This applies to all adults regardless of age. Use our free BMI calculator or weight converter to check your personal healthy weight range and convert between kg and stone.
When should I see my GP about my weight?
See your GP if you're concerned about your weight at any age, have recently gained or lost weight unintentionally, or have weight-related health conditions like high blood pressure or type 2 diabetes. Your GP can assess your individual health and refer you to specialist weight management services if appropriate.
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.