Thrombocytosis or High Platelets


  • Thrombocytosis is a medical condition where the platelets are elevated–platelets are the blood clotting cells in the blood.
  • Thrombocytosis is typically either a reactive process, which is known as a secondary thrombocytosis, or is caused by a myeloproliferative disorder such as essential thrombocythemia.

Thrombocytosis is a medical condition where the platelets are elevated–platelets are the blood clotting cells in the blood. Most cases of thrombocytosis are typically discovered as an incidental laboratory abnormality when a complete BLOOD count is obtained for some unrelated reason, most commonly during a routine medical office visit.

Thrombocytosis causes

Thrombocytosis, megakaryocytes

Thrombocytosis is typically either a reactive process, which is known as a secondary thrombocytosis, or is caused by a myeloproliferative disorder such as essential thrombocythemia (see review and thrombocythemia). Since it is very difficult to differentiate the cause of self-thrombocytosis, specialize laboratory studies are openly indicated in order to arrive at the best possible diagnosis.
Platelets in the bone marrow are derived from the specialized large cells that are known as megakaryocytes, like many other cells in the Bone marrow megakaryocytes need intrinsic chemical factors to stimulate them to maintain the growing potential. Thrombopoietin is the key hormone in the regulation of megakaryocyte, as well as other substances known as cytokines (e.g., Interleukin-6 and interleukin-11). Megakaryocytes and platelets in their surface have specialized structures responding to thrombopoietin which are known as receptors referred to as c–MPL receptors. Thus, when the platelet count drops, increase by the levels of free trouble voiding stimulates megakaryocytes; conversely, when the platelet count rises, reduced levels of free stromal. Avoiding a slow the growth and production of megakaryocytes. This mechanism maintains a platelet production at a steady state. Some patients with liver disorders, reactive thrombocytosis is caused by the production of thrombopoietin by the liver.


How is thrombocytosis diagnosed?

thrombocytosis diagnoses

Detailed history and physical examination to help assess for possible causes, as well as systemic manifestations of blood clots.

Since platelets are very important in hemostasis, an increase in platelet count will predispose blood clots or strokes.

A Blood test or complete blood count determines the number of blood cells, including platelets, in a sample of your blood. In adults, normal platelet count is 150,000 to 450,000 platelets per microliter of blood. If the complete blood count finds you have more than 450,000 platelets, you have thrombocytosis.


How is thrombocytosis treated?

Thrombocytosis treatment

Reactive thrombocytosis is felt to be self-limited with little excess associated thrombotic risk, no antiplatelet therapy is recommended, even for extreme thrombocytosis. 

In patients who present with extreme thrombocytosis of unknown etiology and evidence of active bleeding or critical thrombosis, plateletpheresis can provide a rapid reduction in platelet count while the diagnostic evaluation is undertaken. 

In patients where a clonal cause of thrombocytosis is known or suspected, reducing the risk of thrombotic events in those at risk for them, as thrombosis is the most common complication leading to morbidity and mortality in these disorders. Treatments to this end fall into essentially two categories: 

Cytoreductive therapy with hydroxyurea and anagrelide to decrease circulating platelet count (as well as hematocrit in PV) and antiplatelet therapy, usually in the form of aspirin.


The information in this document does not replace a medical consultation. It is for personal guidance use only. We recommend that patients ask their doctors about what tests or types of treatments are needed for their type and stage of the disease.


  • American Cancer Society
  • The National Cancer Institute
  • National Comprehensive Cancer Network
  • American Academy of Gastroenterology
  • National Institute of Health
  • MD Anderson Cancer Center
  • Memorial Sloan Kettering Cancer Center
  • American Academy of Hematology





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