Dehydration is defined as excessive loss of water from the body. Body requires certain amount of fluid intake daily for normal functions. Minimum daily requirement of water intake is about 1 L. This varies with the age and activity of the individual. The most active individuals need 2 to 3 L of water intake daily. Dehydration occurs when fluid loss is more than what is consumed.


Basically, dehydration is of three types:

1. Mild dehydration: It occurs when fluid loss is about 5% of total body fluids. Dehydration is not very

serious and can be treated easily by rehydration.

2. Moderate dehydration: It occurs when fluid loss is about 10%. Dehydration becomes little serious

and immediate treatment should be given by rehydration.

3. Severe dehydration: It occurs when fluid loss is about 15%. Dehydration becomes severe and

requires hospitalization and emergency treatment. When fluid loss is more than 15%, dehydration

becomes very severe and life threatening. On the basis of ratio between water loss and sodium

loss, dehydration is classified into three types:

1. Isotonic dehydration: Balanced loss of water and sodium as in the case of diarrhea or vomiting.

2. Hypertonic dehydration: Loss of more water than sodium as in the case of fever.

3. Hypotonic dehydration: Loss of more sodium than water as in the case of excess use of diuretics Causes

1. Severe diarrhea and vomiting due to gastrointestinal disorders

2. Excess urinary output due to renal disorders

3. Excess loss of water through urine due to endocrine disorders such as diabetes mellitus, diabetes

insipidus and adrenal insufficiency

4. Insufficient intake of water

5. Prolonged physical activity without consuming adequate amount of water in hot environment

6. Excess sweating leading to heat frustration (extreme loss of water, heat and energy). Severe

sweating and dehydration occur while spending longer periods on regular basis in the saunas

7. Use of laxatives or diuretics in order to lose weight quickly. This is common in athletes.

Signs and Symptoms

Mild and moderate dehydration

1. Dryness of the mouth

2. Excess thirst

3. Decrease in sweating

4. Decrease in urine formation

5. Headache

6. Dizziness

7. Weakness

8. Cramps in legs and arms.

Severe dehydration

1. Decrease in blood volume

2. Decrease in cardiac output

3. Low blood pressure

4. Hypovolemic cardiac shock

5. Fainting.

Very severe dehydration

1. Damage of organs like brain, liver and kidneys

2. Mental depression and confusion

3. Renal failure

4. Convulsions

5. Coma.

Dehydration in Infants

Infants suffering from severe diarrhea and vomiting caused by bacterial or viral infection, develop dehydration. It becomes life threatening if the lost body fluids are not replaced. This happens when parents are unable to recognize the signs.

Aging Effects on Dehydration

Elders are at higher risk for dehydration even if they are healthy. It is because of increased fluid loss and

decreased fluid intake. In some cases, severe dehydration in old age may be fatal.


Treatment depends upon the severity of dehydration. In mild dehydration, the best treatment is drinking of water and stopping fluid loss. However, in severe dehydration  drinking water alone is ineffective because it cannot compensate the salt loss. So the effective treatment for severe dehydration is oral rehydration therapy.

Oral rehydration therapy

Oral rehydration therapy (ORT) is the treatment for dehydration in which a oral rehydration solution (ORS) is administered orally. ORS was formulated by World Health Organization (WHO). This solution contains anhydrous glucose, sodium chloride, potassium chloride and trisodium citrate.

In case of very severe dehydration, proper treatment is the intravenous administration of necessary water and electrolytes.


Water intoxication is the condition characterized by great increase in the water content of the body. It is also called overhydration, hyperhydration, water excess or water poisoning.


Water intoxication occurs when more fluid is taken than

that can be excreted. Water intoxication due to drinking

excess water is rare when the body’s systems are

functioning normally. But there are some conditions that

can produce water intoxication.

1. Heart failure in which heart cannot pump blood


2. Renal disorders in which kidney fails to excrete

enough water in urine

3. Hypersecretion of antidiuretic hormone as in the

case of syndrome of inappropriate hypersecretion

of antidiuretic hormone (SIADH)

4. Intravenous administration of unduly large amount

of medications and fluids than the person’s body

can excrete

5. Infants have greater risk of developing water intoxication in the first month of life, when the filtration

mechanism of the kidney is underdeveloped and cannot excrete the fluid rapidly

6. Water intoxication is also common in children having swimming practice, since they are more prone to

drink too much of water while swimming

7. An adult (whose heart and kidneys are functioning normally) can develop water intoxication, if the

person consumes about 8 L of water everyday regularly.

Signs and Symptoms

1. Since the brain is more vulnerable to the effects of water intoxication, behavioral changes appear first

2. Person becomes drowsy and inattentive

3. Nausea and vomiting occur

4. There is sudden loss of weight, followed by weakness and blurred vision

5. Anemia, acidosis, cyanosis, hemorrhage and shock are also common.

6. Muscular symptoms such as weakness, cramps,

twitching, poor coordination and paralysis develop

7. Severe conditions of water intoxication result in:

i. Delirium (extreme mental condition characterized by confused state and illusion)

ii. Seizures (sudden uncontrolled involuntary muscular contractions)

iii. Coma (profound state of unconsciousness, in which the person fails to respond to external

stimuli and cannot perform voluntary actions).


Mild water intoxication requires only fluid restriction. In very severe cases, the treatment includes:

1. Diuretics to increase water loss through urine

2. Antidiuretic hormone (ADH) receptor antagonists to prevent ADH-induced reabsorption of water from

renal tubules

3. Intravenous administration of saline to restore sodium.

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