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 Height and Age?
Your healthy weight depends on your height, age, and individual health factors rather than age alone. The NHS uses BMI (body mass index) as the main tool to assess whether your weight is healthy for your height, regardless of age. While age can affect metabolism and muscle mass, the same healthy BMI ranges (18.5 to 24.9) apply to most adults. However, factors like physical activity level, muscle mass, and any existing health conditions also matter. Our free BMI calculator above lets you check your personal healthy weight range instantly based on your height.
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 Guidance on Healthy Weight by Height
The NHS recommends using BMI to assess healthy weight for your height, calculated as weight (kg) ÷ height (m)². A healthy BMI falls between 18.5 and 24.9 for most UK adults. For a person 5ft 8in (173cm) tall, a healthy weight ranges from about 55kg to 74kg (8st 9lbs to 11st 8lbs). However, it's important to remember that BMI doesn't account for muscle mass — athletes may have a higher BMI but lower body fat. The NHS also recommends measuring waist circumference alongside BMI, as where fat is stored matters for health: men should aim for under 94cm (37in), women under 80cm (31.5in). Age itself doesn't change these BMI categories, though older adults may naturally have less muscle. Use our weight converter above to check your specific height in different units, then calculate your BMI using the free BMI calculator on this page.
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.
Weight Changes Across Different Life Stages
Weight naturally fluctuates throughout life due to changes in metabolism, muscle mass, hormone levels, and physical activity. During childhood and adolescence, growth charts rather than adult BMI categories apply — parents should consult NHS resources for children's healthy weight. In adulthood, metabolic rate gradually slows, meaning some people find weight management more challenging from their 30s onwards. Pregnancy and menopause also affect weight and body composition significantly. Regardless of age, sustainable weight management involves balanced nutrition and regular physical activity. If you're concerned about your weight in relation to your health, your GP can provide personalised advice considering your individual circumstances, medical history, and any health conditions.
- 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 age affect healthy weight?
Age itself doesn't change the healthy BMI range (18.5–24.9), but it can affect metabolism and muscle mass. Metabolic rate gradually slows with age, and muscle naturally decreases, which can make weight management feel more challenging. However, the same BMI categories apply. Your GP can give personalised advice considering your age and health.
What's the healthy weight for a 5ft 8in tall person?
For someone 173cm (5ft 8in) tall, a healthy weight ranges from approximately 55kg to 74kg (8st 9lbs to 11st 8lbs), based on a BMI of 18.5–24.9. This applies to most adults regardless of age. Use our free BMI calculator above to check your specific height and weight instantly.
Is BMI accurate for assessing healthy weight?
BMI is a useful screening tool but has limitations — it doesn't distinguish between muscle and fat, so very muscular people may have a high BMI with low body fat. The NHS recommends using BMI alongside waist circumference measurement for a more complete picture of health risk.
How does weight management differ by age?
Younger adults may find weight loss easier due to higher metabolic rate, while older adults may need to focus more on muscle-preserving exercise. Hormonal changes during menopause or andropause affect weight distribution. Regardless of age, sustainable weight loss involves a balanced diet, regular activity, and often GP support.
Should I aim for the same weight as someone else my height?
No — healthy weight varies by individual factors including muscle mass, bone density, genetics, and overall health. Two people of the same height and age can have different healthy weight ranges. Your GP can help determine what's healthy for you personally using the free weight converter and BMI calculator on this page.
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.