The Science of Dehydration

Dehydration and the Elderly

Risks of Dehydration in the Elderly

Older people are more likely to experience dehydration. The greatest risk factor for dehydration in the elderly is poor intake of fluids.

Older people are at an increased risk of dehydration, due to:

  • Decreased thirst reflex with age.
  • Changes in kidney function with age.
  • Less fluid in the body with age
  • Inability to obtain water due to physical immobility or medical conditions (such as dementia).

Common Signs of Dehydration in the Elderly

Older people will also experience the usual signs and symptoms of dehydration.

Common symptoms of dehydration include:

  • Sticky or dry mouth
  • Increased thirst
  • Fatigue
  • Dizziness
  • Headache
  • Dark yellow or decreased urine output

There are a few more useful indicators of dehydration in the elderly. These include:

  • Reduced sweating under the arms

TIP – place some tissue paper under the arms for a few minutes. If the paper does not moisten, the person may be dehydrated.

  • Reduced skin elasticity.
  • Dry mouth and tongue.
  • Darker urine than usual.

Fluid Requirements for the Elderly

Due to the increased risk of dehydration, it is recommended that older people consume more fluid than younger people:

For older people:

  • 100 mL fluid per kg body weight for first 10 kg
  • 50 mL fluid per kg body weight for next 10 kg
  • 15 mL fluid per kg body weight for each kg after 20 kg

The following table provides a quick reference for the recommended fluid intake for the elderly, based on weight:

Patient Weight (kg) ?30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105
Fluid requirement (litres/day) 1.7 1.7 1.8 1.9 2.0 2.0 2.1 2.2 2.3 2.3 2.4 2.5 2.6 2.6 2.7 2.8


Prevention of Dehydration in the Elderly

It is important that older people are well aware of the signs and symptoms of dehydration. If any signs or symptoms of dehydration are present, it is best to start treatment as soon as possible, to prevent worsening of this condition.

Strategies to maintain or increase fluid intake:

  • Be well aware of signs and symptoms of dehydration and monitor for these.
  • Consume fluids on a regular basis (e.g. every 1.5 hours by day).
  • Consume fluids at routine events, such as before or after showering.
  • Try to consume wet foods such as jelly and custard, as these add to the daily fluid volume.

Consume 100-200 mL of Hydralyte when taking regular medications.

Treatment of Dehydration in the Elderly

When treating dehydration in the elderly, the use of an oral fluid intake chart may be useful to measure fluid intake and losses. This chart may be most useful in an aged care facility. [Link to oral fluid intake chart].

Aged Care Guidelines

There are over 160,000 Australians in aged care services (as at June 2010). Many of these residents are either physically or cognitively impaired.

There has been some public concern around the quality of care in aged care facilities. Evidence has shown that two indicators of inadequate care are poor nutrition and inadequate hydration.

In July 2012, Professor Michael Woodward (Medical Director, Aged and Residential Care Services, Heidelberg Repatriation Hospital) released ‘Guidelines to effective hydration in aged care facilities’. These guidelines are designed as a practical tool for aged care facility staff, so they can better manage one aspect of quality care – prevention and treatment of dehydration.

If you would like to receive copies of the ‘Guidelines to effective hydration in aged care facilities, please e-mail

Travel Tips for the Elderly

Older travellers are more likely to have chronic conditions and special needs. Additionally, international holidays can be physically demanding, and injuries are more common in the older population.

When travelling it is important elderly people remain well hydrated – consume plenty of fluid (such as water and Hydralyte) and avoid alcohol and caffeine.

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