Large platelets are those with a platelet diameter of more than 10 μm. The percentage of large platelets in normal people is 8%-16%. The most common diseases that reduce the ratio of large platelets are the various causes of bone marrow hematopoietic disorders, such as aplastic anemia, where the ratio of large platelets is significantly reduced due to bone marrow hematopoietic failure and failure of megakaryocytes to divide normally. In addition more than half of patients with leukemia also have a reduced large platelet ratio due to destruction of normal bone marrow hematopoietic function. If the ratio of large platelets is getting lower, it is often one of the signs of gradual decline of bone marrow hematopoietic function. Also leukemia patients with bone marrow suppression after chemotherapy have a reduced ratio of large platelets, but if the ratio of large platelets starts to increase, it marks the beginning of remission of bone marrow suppression.