A low red blood cell count is anemia. There are three most common causes of low erythrocyte count: first, reduced erythropoiesis, common diseases include aplastic anemia, pure red blood cell aplastic anemia, congenital abnormal erythropoietic anemia, hematopoietic microenvironment-induced erythropoietic reduction is common in bone marrow necrosis, myelosclerosis, acute leukemia, multiple myeloma, etc.; while hematopoietic material deficiency-induced erythropoietic reduction are Iron deficiency anemia, megaloblastic anemia. Second, excessive destruction of red blood cells, common diseases include autoimmune hemolytic anemia, thalassemia, sericosis and other immune system diseases caused by hemolytic anemia. Third, chronic blood loss, common are peptic ulcer bleeding, hemorrhoid bleeding or gynecological disease bleeding, etc.