Possible causes of elevated blood ammonia in children include physiological factors such as diet, and pathological factors such as liver damage, which can be dangerous if not intervened in time. Normal people have a certain amount of ammonia in the blood, the concentration of which is about 18~72μmol/L. Ammonia in the blood comes from the absorption of the digestive tract after diet, especially protein diet; on the other hand, it also comes from plasma proteins and other plasma proteins in the body, which are metabolized by the liver. Elevated blood ammonia in children is transient and usually not dangerous if it is caused by eating a high protein diet. In addition to physiological factors, liver damage diseases such as cirrhosis, hepatocellular carcinoma, severe hepatitis, gastrointestinal bleeding, and ammonia elimination disorders caused by renal impairment may also cause elevated blood ammonia, which, if not intervened in a timely manner, may result in ammonia encephalopathy, which can be life-threatening and is more dangerous. Children with elevated blood ammonia are advised to seek prompt medical attention.