The common causes of anemia are: first, poor hematopoietic function, some chemical, physical, toxic, or other unknown factors that affect the hematopoietic function of the bone marrow, anemia can occur, and this anemia often also causes a decrease in blood white blood cells and platelets; second, the lack of hematopoietic substances, hematopoietic substances, including vitamin B12, folic acid, iron Lack of any of these substances can cause anemia; third, increased destruction of red blood cells, some congenital diseases or acquired factors that cause shortening of the life span of red blood cells and accelerated destruction can cause anemia, the most common is hemolytic anemia; fourth, blood loss, such as peptic ulcers, tumors of the digestive tract, rupture of esophageal varices caused by cirrhosis, and Drugs causing damage to the gastric mucosa, recurrent blood in the stool from ulcerative colitis, hemorrhoids, etc. can all cause acute and chronic blood loss, which eventually causes anemia.