Dehydration is a clinical state due to the loss of water and solutes; in adults the causes of this clinical state are diverse: gastrointestinal and renal losses, skin alterations (burns) or sequestration of the third space (fractures). The diagnosis is clinical, the signs and symptoms determine the degree of dehydration and the treatment to be implemented. In this work a review is made on the physiology, pathophysiology, clinical picture and therapeutic treatment of the adult patient, since there is little literature directed to this age group. Keywords: Dehydration; adult; water; electrolytes."