Medical causes of dehydration in humans - Dehydration

In humans, dehydration can be caused by a wide range of diseases and states that impair water homeostasis in the body. These include:

External or stress-related causes
Prolonged physical activity without consuming adequate water, especially in a hot and/or humid environment
Prolonged exposure to dry air, e.g. in high-flying airplanes (5-12% relative humidity)
Survival situations, especially desert conditions
Blood loss or hypotension due to physical trauma
Diarrhea
Hyperthermia
Shock (hypovolemic)
Vomiting
Burns
Lacrimation
Use of Methamphetamine, Amphetamine and other stimulants.
Drinking of Alcohol. (In place of water)
Infectious diseases
Cholera
Gastroenteritis
Shigellosis
Yellow fever
Malnutrition
Electrolyte disturbance
Hypernatremia (also caused by dehydration)
Hyponatremia, especially from restricted salt diets
Fasting
Recent rapid weight loss may reflect progressive depletion of fluid volume (the loss of 1 L of fluid results in a weight loss of 1 kg or 2.2 lb).[1]
Patient refusal of nutrition and hydration
Other causes of obligate water loss
Severe hyperglycemia, especially in Diabetes mellitus
Glycosuria