Oral rehydration salts are given orally to prevent or treat dehydration due to acute diarrhoea. Essential water and salts are lost in stools and vomiting, and dehydration results when blood volume is decreased because of fluid loss from the extracellular fluid compartment. Preservation of the facilitated glucose-sodium co-transport system in the small-bowel mucosa is the rationale of oral rehydration therapy. Glucose is actively absorbed in the normal intestine and carries sodium with it in about an equimolar ration. Therefore, there is a greater net absorption of an isotonic salt solution with glucose than one without it.