After chemotherapy, because chemotherapy drugs can inhibit bone marrow hematopoietic function, platelets are usually reduced. High platelets after chemotherapy may be seen in the following situations: First, the chemotherapy regimen contains glucocorticoid drugs, such as dexamethasone and prednisone, which can lead to high platelets in the first few days after stopping chemotherapy. Second, frequent vomiting and inability to eat, resulting in blood concentration. After chemotherapy, due to the side effects of the patient’s violent vomiting and inability to eat and water, the body’s intake of water is obviously insufficient, the blood is concentrated, and the number of platelets detected will be increased. Third, after chemotherapy, the patient’s body is weak and infection occurs, which can lead to a temporary increase in platelets. In conclusion, high platelets after chemotherapy are mostly caused by chemotherapy side effects, which are usually temporary and will soon result in a decrease in platelets, and close attention should be paid to monitoring.