High platelet count PLT may be due to: platelet count reactive increase or primary increase. 1. Platelet count reactive increase is common in: acute hemolysis, acute infection, some tumor patients. 2. Primary increase in platelet count is common in myeloproliferative diseases such as chronic granulocytic leukemia, early stage of myelofibrosis, primary thrombocythemia and true erythrocytosis. Platelet count PLT is an indicator in routine blood tests, which is measured by an automated blood cell analyzer to count the number of platelets per unit volume (L) of surrounding blood. The primary function of platelets is to aggregate to prevent the body’s tissues from breaking down and bleeding. The normal range of platelet count should be (100~300)×10⁹/L. Clinically, a platelet count greater than 300×10⁹/L is called an increased platelet count. Specific disease diagnosis and treatment under the guidance of a physician.