Understanding Dehydration


Dehydration – The Facts



The human body consists of 50 to 75 percent water which forms the basis of blood, urine, digestive fluids and perspiration; water is also contained in fat, bones and lean muscle. Because the human body cannot store water we need to drink daily to replenish what is lost. The amount we need to drink depends on things like the size of our body, activity levels, metabolism, the weather and the foods we eat.


  • Without food humans can survive for weeks, without water humans can survive for days
  • Men have higher water content than women
  • Body water content gets lower as we get older
  • The average adult will lose around 2.5 – 3 liters of water per day; this will increase with things like hot weather and/or exercise
  • The average elderly person will lose around two liters per day
  • A person who travels by airplane can lose up to 1.5 liters of water in a three hour flight


What Does Water Do For The Body?

Water Is Needed To:

  • Maintain good cellular health and integrity
  • Keep the bloodstream thin enough to flow through blood vessels
  • Help in eliminating waste products from the body
  • Regulate body temperature (via sweating)
  • Keep mucous membranes moist such as those of the mouth and lungs
  • Cushion and lubricate joints
  • Keep the bladder clear of bacteria and reduce the risk of cystitis
  • Prevent constipation and aid digestion
  • Moisturize the skin
  • Deliver oxygen and nutrients to cells
  • Act as a shock absorber in the spinal cord, the eyes and the amniotic sac during pregnancy


Water In Food

  • Even hard, dry looking foods contain water. In fact the body gets around 20 percent of its water requirements from food
  • Water is also a byproduct of the digestion process and this will provide up to 10 percent of the body’s water requirements
  • The other 70 percent must be supplied via external fluids


Recommended Daily Fluid Intake

Due to the many variables in the amount of fluid the human body can lose per day these amounts are an approximate adequate daily intake in liters per day.

  • Infants 0 to 6 months – 0.7 liters (from formula or breast milk)
  • Infants 7 to 12 months – 0.9 liters (from formula, breast milk and other foods)
  • Children 1 to 3 years – 1.0 liters
  • Children 4 to 8 years – 1.2 liters
  • Girls 9 to 13 years – 1.4 liters
  • Boys 9 to 13 years – 1.6 liters
  • Girls 14 to 18 years 1.6 liters
  • Boys 14 to 18 years 1.9 liters
  • Women – 2.1 liters
  • Men – 2.6 liters

Although fluid intake can come from any fluid, plain, clean water is preferable. (Except in infants on formula or breast milk)


You May Need To Increase Fluid Intake If You Are:

  • On a high protein or high fiber diet (to help prevent constipation)
  • Pregnant or breast feeding
  • Have diarrhea or vomiting
  • Are exposed to hot conditions
  • Are physically active


An inadequate fluid intake can lower your physical and mental abilities, increase the risk of kidney stones and urinary tract infections and make you dehydrated.


Signs of dehydration

  • Headaches
  • Thirst (a late sign of dehydration)
  • Dark colored urine
  • Dry or cracked lips
  • Dry nasal passages
  • Tiredness
  • Lethargy
  • Weakness
  • Mood changes and impaired responses
  • Confusion and hallucinations

In prolonged dehydration urination stops and the kidneys can no longer remove toxic waste from the body. In severe cases this can result in death.


Causes of dehydration

Many factors can cause dehydration including:

  • Low fluid intake
  • Increased sweating; this may be due to hot or humid weather, exercise or fever.
  • Increased urine output
  • Diarrhea
  • Vomiting
  • Recovering from burns


Elderly people are often more at risk of dehydration due to:

  • Problems with their body’s signaling mechanism, they may be dehydrated without feeling thirsty.
  • Declining kidney function
  • Hormonal changes
  • Medications such as laxatives and diuretics
  • Chronic illness and limited mobility


Dehydration in babies and children

Dehydration in children can be a life threatening condition, if you notice any signs or symptoms of dehydration call an ambulance or take your child to the nearest hospital emergency room immediately.

Children are very susceptible to dehydration, especially if they are sick. Diarrhea, Vomiting and fever can quickly dehydrate a baby. 


Symptoms Of Dehydration In A Child May Include:

  • Cold skin
  • Dry mouth
  • A blue tinge to the skin lips and face
  • Lethargy
  • Depressed fontanelle (the soft spot on top of the baby’s head where the bones haven’t closed yet