Water intoxication is the entry of too much water into the cells, resulting in excess water in the cells, also known as dilutional hyponatremia. Water intoxication can be divided into acute water intoxication and chronic water intoxication. Generally, the degree of water intoxication is relatively mild, and the symptoms will be corrected by stopping the continued intake of water and then excreting the excess water from the body, while severe cases can lead to permanent neurological damage or death. The presence of water intoxication can be determined by clinical manifestations, as well as laboratory tests. If the patient has symptoms such as headache, blurred vision, disorientation, or even coma, and after laboratory tests, if the plasma osmolality is below 280 mmol/L, the blood sodium is below 130 mmol/L, or the urine sodium value is >20 mmol/L, the diagnosis of water intoxication can be confirmed. The onset of water intoxication, the rate of decrease in plasma, osmolarity and serum sodium concentration is more important for the clinical presentation of the patient than the actual decrease in value.