Large platelets are those with a platelet diameter greater than 10 microns. The proportion of large blood vessels in the peripheral blood of a normal person is 8%-16%. Low values of large platelets are commonly seen in myelodysplastic disorders, the most common being aplastic anemia. Aplastic anemia is caused by damage to hematopoietic stem cells and a decreased ability to produce megakaryocytes, resulting in an impairment of platelet production, producing smaller size platelets and reduced production of larger size platelets. If the treatment of aplastic anemia is effective, the percentage of large platelets will gradually increase. In addition, the reduction of large platelet ratio can also be seen in patients with acute myeloid leukemia. Due to the massive proliferation of leukemia cells in the bone marrow, normal hematopoiesis is inhibited, and the situation of low large platelet ratio also occurs, and after chemotherapy treatment, the low large platelet ratio will gradually improve.