Anemia is not an independent disease, many diseases can lead to anemia, so the causes of different types of anemia are different, as follows: 1. Iron deficiency anemia: This is by far the most common type of anemia, mainly due to iron deficiency, the most common cause of iron deficiency is chronic blood loss, such as women with long-term increased menstrual flow or with long-term chronic bleeding hemorrhoids, can lead to iron deficiency anemia 2. aplastic anemia: a bone marrow failure disease, mainly due to immune factors. 3. megaloblastic anemia: mainly due to a lack of folic acid or vitamin B12. 4. hypersplenism: can also lead to anemia, the most common cause being liver cirrhosis.