Overhydration, also called water excess or water intoxication, is a
condition in which the body contains too much water.
Overhydration occurs when the body takes in more water than it excretes
and its normal sodium level is diluted. This can result in digestive
problems, behavioral changes, brain damage, seizures, or coma. An adult
whose heart, kidneys, and pituitary gland are functioning properly would
have to drink more than two gallons of water a day to develop water
intoxication. This condition is most common in persons whose kidney
function is impaired and may occur when doctors, nurses, or other
healthcare professionals administer greater amounts of water-producing
fluids and medications than the person's body can excrete.
Infants seem to be at greater risk for developing overhydration. The
Centers for Disease Control and Prevention has declared that babies are
especially susceptible to oral overhydration during the first month of
life, when the kidneys' filtering mechanism is too immature to
excrete fluid as rapidly as older infants do. Breast milk or formula
provides all the fluids a healthy baby needs. Water should be given
slowly, sparingly, and only during extremely hot weather. Overhydration,
which has been cited as a hazard of infant swimming lessons, occurs
whenever a baby drinks too much water, excretes too little fluid, or
consumes and retains too much water.
Overhydration is the most common electrolyte imbalance in hospitals,
occurring in about 2 percent of all people.
Causes and symptoms
Drinking too much water rarely causes overhydration when the body's
systems are working normally. People with heart, kidney, or liver disease
are more likely to develop overhydration because their kidneys are unable
to excrete water normally. It may be necessary for people with these
disorders to restrict the amount of water they drink and/or adjust the
amount of salt in their diets.
Since the brain is the organ most susceptible to overhydration, a change
in behavior is usually the first symptom of water intoxication. The person
may become confused, drowsy, or inattentive. Shouting and delirium are
common. Symptoms of overhydration may include blurred vision,
and twitching, paralysis on one side of the body, poor coordination,
nausea and vomiting
, rapid breathing, sudden weight gain, and weakness. The person's
complexion is normal or flushed. Blood pressure is sometimes higher than
normal, but elevations may not be noticed even when the degree of water
intoxication is serious.
Overhydration can cause acidosis (a condition in which blood and body
tissues have an abnormally high acid content), anemia, cyanosis (a
condition that occurs when oxygen levels in the blood drop sharply),
hemorrhage, and shock. The brain is the organ most vulnerable to the
effects of overhydration. If excess fluid levels accumulate gradually, the
brain may be able to adapt to them, and the person will have only a few
symptoms. If the condition develops rapidly, confusion, seizures, and coma
are likely to occur.
A doctor should be called when a person becomes confused, drowsy, or
inattentive. Persons should also consider calling a doctor when a person
experiences blurred vision, muscle cramps and twitching, paralysis on one
side of the body, poor coordination, nausea and vomiting, rapid breathing,
sudden weight gain, or weakness.
Before treatment can begin, a doctor must determine whether an
individual's symptoms are due to overhydration, in which excess
water is found within and outside cells, or excess blood volume, in which
high sodium levels prevent the body from storing excess water inside the
cells. Overhydration is characterized by excess water both within and
around the body's cells, while excess blood volume occurs when the
body has too much sodium and cannot move water to reservoirs within the
cells. In cases of overhydration, symptoms of fluid accumulation do not
usually occur. On the other hand, in cases of excess blood volume, fluid
tends to accumulate around cells in the lower legs, abdomen, and chest.
Overhydration can occur alone or in conjunction with excess blood volume,
and differentiating between these two conditions may be difficult.
Mild overhydration can generally be corrected by following a
doctor's instructions to limit fluid intake. In more serious cases,
diuretics may be prescribed to increase urination, although these drugs
tend to be most effective in the treatment of excess blood volume.
Identifying and treating any underlying condition (such as impaired heart
or kidney function) is a priority, and fluid restrictions are a critical
component of every treatment plan.
In people with severe neurologic symptoms, fluid imbalances must be
corrected without delay. A powerful diuretic and fluids to restore normal
sodium concentrations are administered rapidly at first. When the person
has absorbed 50 percent of the therapeutic substances, blood levels are
measured. Therapy is continued at a more moderate pace in order to prevent
brain damage as a result of sudden changes in blood chemistry.
—A bluish tinge to the skin that can occur when the blood oxygen
level drops too low.
—Salts and minerals that produce electrically charged particles
(ions) in body fluids. Common human electrolytes are sodium chloride,
potassium, calcium, and sodium bicarbonate. Electrolytes control the
fluid balance of the body and are important in muscle contraction,
energy generation, and almost all major biochemical reactions in the
—A medical emergency in which the organs and tissues of the body
are not receiving an adequate flow of blood. This deprives the organs
and tissues of oxygen and allows the build-up of waste products. Shock
can be caused by certain diseases, serious injury, or blood loss.
People should be careful not to drink excessive amounts of water. Persons
with impaired kidney function must exert extra caution.
, a tendency to retain water, and kidney diseases and disorders increase
the likelihood of a person's becoming overhydrated. Infants and the
elderly seem to be at increased risk for overhydration, as are people with
certain mental disorders or
Greenbaum, Larry A. "Electrolytes and Acid-Base Disorders."
Nelson Textbook of Pediatrics
, 17th ed. Edited by Richard E. Behrman et al. Philadelphia: Saunders,
2003, pp. 191–241.
Horne, Mima M.
Pocket Guide to Fluid, Electrolyte, and Acid-Base Balance
, 5th ed. Amsterdam: Elsevier Science, 2004.
Kokko, Juha P. "Fluids and Electrolytes." In
Cecil Textbook of Medicine
, 22nd ed. Edited by Lee Goldman et al. Philadelphia: Saunders, 2003, pp.
Singer, Gary G., and Barry M. Brenner. "Fluid and Electrolyte
Harrison's Principles of Internal Medicine
, 15th ed. Edited by Eugene Braunwald et al. New York: McGraw-Hill, 2001,
American College of Sports Medicine.
401 W. Michigan St., Indianapolis, IN 46202–3233. Web site:
"Dehydration and fluid maintenance."
National Guideline Clearinghouse.
Available online at
(accessed January 7, 2005).
Available online at
January 7, 2005).
Virtual Naval Hospital.
Available online at
January 7, 2005).