Older Adult Hydration Calculator

Why older adults are at greater risk of dehydration

The physiological drivers of dehydration risk in older adults are well documented. Total body water decreases with age — from roughly 60% in young adults to around 50% in those over 75 — reducing the reserve against fluid loss. The thirst mechanism diminishes with age, meaning older adults often do not feel thirsty until dehydration is already established. Kidney function declines, reducing the ability to concentrate urine and conserve water.

Additional factors include reduced mobility limiting access to fluids, cognitive decline affecting awareness of thirst and drinking behaviour, medication effects (diuretics are common in this age group), and deliberate fluid restriction to manage urinary incontinence.

Practical strategies for older adults

The most effective strategy is proactive drinking on a schedule rather than waiting for thirst. Keeping a glass of water on the table during meals and at fixed points during the day, setting hourly reminders, and counting all fluid-containing foods and drinks (soups, custards, soft fruits) towards the daily target are all evidence-supported approaches.