Dehydration is defined as excessive loss of water from the body. The most active individuals need 2 to 3 L of water intake daily. Dehydration occurs when fluid loss is more than what is consumed.


 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.

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.


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. 


  • 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.