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
Weight Versus Height and Age — UK Context
Understanding healthy weight ranges for your height and age is essential for UK health management. Unlike fixed weight targets, the NHS uses BMI (body mass index) to assess whether weight is healthy relative to height — a more accurate approach that accounts for individual body composition. Age also affects weight distribution and muscle mass, which is why health guidance varies across the lifespan. This guide explains UK health standards, how to use your height to determine a healthy weight range, and why age matters for weight assessment.
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 Guidelines for Healthy Weight by Height
In the UK, the NHS uses BMI rather than age-specific weight charts to determine healthy weight ranges. BMI is calculated by dividing your weight in kilograms by your height in metres squared. A healthy BMI ranges from 18.5 to 24.9 for most UK adults, regardless of age.
To calculate your healthy weight range for your height, use this formula: multiply your height in metres squared by 18.5 (lower bound) and 24.9 (upper bound). For example, at 1.73m (5ft 8in), a healthy weight range is approximately 55–74 kg (8st 10lbs to 11st 10lbs).
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds: a healthy BMI of 18.5 to 22.9. This is because these populations face higher health risks from obesity at lower BMI levels. Age alone does not change BMI thresholds, though body composition naturally changes with age — muscle typically decreases and fat distribution shifts.
Use our free BMI calculator above to find your personal BMI and healthy weight range instantly based on your height.
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.
Age, Weight, and Health — What Changes Over Time
While BMI thresholds remain constant across adulthood, how weight affects health does change with age. Younger adults typically have more muscle mass, so weight is distributed differently than in older adults. From around age 30, most people naturally lose approximately 3–5% of muscle per decade — meaning the same weight may represent more body fat at age 60 than at age 30.
The NHS also recognises that waist circumference becomes increasingly important with age. Central fat storage (around the abdomen) carries greater health risks, particularly for cardiovascular disease and type 2 diabetes. Men should maintain a waist circumference below 94cm (37in) for lower risk, and women below 80cm (31.5in). This matters more in older age when fat distribution naturally shifts towards the centre. Regular weight monitoring and maintaining a healthy weight management routine becomes more important in midlife and beyond to preserve health and mobility.
- 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.
Is there a specific weight chart for different ages in the UK?
No — the NHS uses BMI thresholds that are the same for all adults regardless of age. A healthy BMI is 18.5–24.9 for most people. However, body composition changes with age (muscle decreases, fat distribution shifts), so the same weight may represent different health profiles at different ages. Your GP can assess your individual health status.
What is the healthy weight range for a woman of 5ft 5in (165cm)?
At 165cm, a healthy BMI range (18.5–24.9) corresponds to approximately 50–67 kg (7st 12lbs to 10st 7lbs). However, if you're of South Asian or Black African/Caribbean heritage, the healthy range is narrower: 18.5–22.9 BMI, approximately 50–61 kg (7st 12lbs to 9st 8lbs). Use our BMI calculator above for your exact range.
Why does weight distribution change with age?
From age 30 onwards, most people lose approximately 3–5% of muscle mass per decade. This causes the body to store more fat, often shifting towards the abdomen (central fat). Hormonal changes, particularly during and after menopause in women, also affect fat distribution. This is why waist circumference becomes increasingly important for health assessment in older adults.
Is a weight chart based on height and age more accurate than BMI?
Not necessarily. The NHS considers BMI the standard screening tool for adults because it accounts for individual height proportions. However, BMI has limitations — it doesn't distinguish muscle from fat. Your GP may also assess waist circumference and overall health context, which age and individual factors do influence.
Should I aim for the lower or upper end of my healthy weight range?
Both the lower and upper ends of your healthy BMI range (18.5–24.9) are healthy. Where you sit within this range depends on factors like muscle mass, bone density, and personal health goals. Your GP can advise on what's healthiest for your individual circumstances.
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.