Acute gastroenteritis is an acute diffuse lesion of the intestinal tract caused by various reasons, often with a history of improper diet, and the patient shows symptoms of nausea and vomiting with dehydration. The specific amount of rehydration needs to be decided according to the patient’s dehydration and the severity of the disease. Mild dehydration suggests a previous loss of 1000 ml, which should be supplemented with 1000 ml of the lost amount, while if the patient is eating poorly, the physiological requirement of 2000 ml of fluid should be supplemented. If the patient is nauseous, poorly fed and still dehydrated, it is necessary to continue to replenish the lost amount of fluids to maintain the patient’s normal blood pressure, and the replenished fluids are usually salt first and then sugar or alternating between sugar and salt.