Low white blood cells and hemoglobin refer to the number of white blood cells and hemoglobin concentration in the peripheral blood that are below the normal range. The common causes of low white blood cells and hemoglobin are: i. Bone marrow hematopoietic failure diseases, the most common disease is aplastic anemia, due to the damage of hematopoietic stem cells, which cannot produce sufficient number of blood cells and can cause the condition of lower concentration of white blood cells and hemoglobin in peripheral blood. Secondly, it is common in patients with malignant tumors after receiving radiation therapy and chemotherapy. Due to the damage of hematopoietic stem cells by radiation therapy and chemotherapy, the condition of reduced leukocytes and hemoglobin in peripheral blood can also occur. Third, when there is a severe deficiency of hematopoietic raw materials, such as in patients with severe iron deficiency anemia, and in patients with severe deficiency of folic acid and vitamin B12, a decrease in leukocytes and hemoglobin may also occur due to the lack of hematopoietic raw materials and the inability to produce a variety of normal blood cells.