A high platelet count is when the number of platelets in the peripheral blood exceeds the normal range. There are two causes of high platelet count: the first cause is called reactive platelet count, which refers to the increase in platelet count caused by external factors, such as infection, bleeding, trauma, surgery, etc., which can cause a reactive increase in platelet count, especially in major surgery where there is a significant increase in platelet count. The second cause, primary thrombocytosis, the most common type of disease is primary thrombocytosis, where the number of platelets can appear abnormally high. In some of these hematologic disorders, such as leukemia, after chemotherapy, the patient enters a myelosuppressive phase with a decrease in whole blood cells in the peripheral blood. However, after the remission of the myelosuppression phase, the platelet count can rebound and often appears abnormally high, which is a normal phenomenon.