If you are too thin, you may consider consulting a gastroenterologist or endocrinologist. Because the common cause of too thin people, on the one hand, is the gastrointestinal malabsorption, and on the other hand, is the self-consumption of too much. If you lose weight quickly in a short period of time, you can also hang up the oncology department. When the gastrointestinal malabsorption, it will lead to too thin. This belongs to the diagnosis and treatment of gastroenterology, for example, to exclude the existence of chronic atrophic gastritis, cholecystitis, pancreatitis and so on. When there is an auto-wasting disease, such as hyperthyroidism or diabetes, it can also cause a person to become too thin. Hyperthyroidism and diabetes mellitus are treated in the endocrinology department. Rapid thinning in a short period of time, should also consider the tumor disease caused by oncology, you can hang up oncology for examination and clarification. There is also a part of people with thin body belongs to congenital, and has family aggregation. It is recommended to go to the hospital for examination to clarify whether there is a disease that causes it.