BMI Calculator for Older Adults guide
BMI Calculator for Older Adults: BMI and Malnutrition Risk
Use our BMI calculator for older adults to check BMI and malnutrition risk with the MUST screening tool, and find out why weight loss matters more in later life.
By the AllCalculator editorial teamUpdated 16 October 20262 min read
For most adults, the worry with weight is carrying too much. But in later life, being underweight and losing weight without trying are often bigger risks. Our BMI Calculator for Older Adults works out your BMI and screens for malnutrition using the tool the NHS uses.
How to use the calculator (BMI Calculator for Older Adults)
- Enter height and weight, in metric or imperial.
- Optionally, enter weight 3 to 6 months ago, to check for unplanned weight loss.
- Say whether the person is acutely ill and has had, or is likely to have, little or no food for more than 5 days.
You'll see the BMI, the score for each step of MUST and the overall risk.
How MUST works
MUST (the Malnutrition Universal Screening Tool) was developed by BAPEN and is used in hospitals, care homes and GP surgeries across the UK. It has three steps:
| Step | Score 0 | Score 1 | Score 2 |
|---|---|---|---|
| 1. BMI | Over 20 | 18.5 to 20 | Under 18.5 |
| 2. Unplanned weight loss in 3–6 months | Under 5% | 5% to 10% | Over 10% |
| 3. Acutely ill, no food for over 5 days | No | — | Yes |
The scores are added up:
- 0: low risk
- 1: medium risk
- 2 or more: high risk
A worked example
With the calculator's default settings, someone who is 165cm tall and weighs 62kg, down from 66kg a few months ago, has a BMI of 22.8 (score 0) but has lost 6.1% of their weight (score 1). Their MUST score is 1, so they're at medium risk, and their weight is worth keeping an eye on.
Why BMI is different in later life
The BMI categories are the same for all adults, but research suggests the healthiest BMI may be a little higher in later life. A 2014 review of studies of people aged 65 and over found that the risk of death rose at BMIs below about 23, but being overweight wasn't linked to a higher risk, and risk only rose again above 33.
Muscle naturally decreases with age, so keeping active and eating enough protein are important.
Signs of malnutrition
- Losing weight without trying, or clothes, rings or dentures becoming loose
- Tiredness and weakness
- Getting ill more often or taking longer to recover
- Losing interest in food
Frequently asked questions
Is it normal to lose weight as you get older?
Some changes in body composition are normal, but unplanned weight loss isn't, and should be checked by a GP.
Should older people try to lose weight?
Only with advice from a health professional. Losing weight in later life can mean losing muscle, which affects strength and balance.
What if I can't measure height?
Health professionals can estimate it from forearm (ulna) length. To check BMI on its own, use our BMI Calculator.
Sources and further reading
- BAPEN: The Malnutrition Universal Screening Tool (MUST)bapen.org.uk
- NHS: Malnutritionnhs.uk
- Winter and others (2014): BMI and all-cause mortality in older adultspubmed.ncbi.nlm.nih.gov
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This guide is general information to help you understand your options. It isn't financial, tax, legal or building advice and doesn't take your personal circumstances into account. Figures were checked when the guide was last updated and can change, so confirm anything important with GOV.UK, HMRC, a regulated adviser or a qualified tradesperson.