Platelets of 590×10⁹ are considered high. Normal counts range from (100 to 300) x 10⁹ platelets per liter of blood, but further testing is usually considered only if the upper limit exceeds 300×10⁹ /L. Platelets of 590×10⁹ are considered significantly elevated and further testing is recommended to determine the cause. Elevated platelet concentrations are called thrombocytosis and may be congenital, reactive, or due to unregulated production such as myeloproliferative neoplasms or certain other myeloid tumors. There is an increased risk of thrombosis in some patients with thrombocytosis. Therefore, if the clinical findings of platelets are higher than normal, it is necessary to actively seek medical attention, and under the guidance of the clinician to decide whether it is necessary to carry out further investigations to clarify the cause of the disease or regular review and follow-up.