Bone marrow — spongy tissue inside your bones — contains stem cells that can become red blood cells, white blood cells or platelets. Platelets travel through your blood vessels. They stick together to form clots that stop the bleeding when you damage a blood vessel, such as when you get a cut. A normal platelet count ranges from 150,000 to 450,000 platelets per microliter of blood.

If you have thrombocytosis caused by a bone marrow disorder (essential thrombocythemia), your bone marrow overproduces the cells that form platelets (megakaryocytes), releasing too many platelets into your blood. If your blood test results reveal a high platelet count, it's important for your doctor to determine whether you have essential thrombocythemia or reactive thrombocytosis.

Reactive thrombocytosis causes include:

  • Acute bleeding and blood loss
  • Allergic reactions
  • Cancer
  • Chronic kidney failure or another kidney disorder
  • Exercise
  • Heart attack
  • Infections
  • Iron deficiency anemia
  • Removal of your spleen
  • Hemolytic anemia — a type of anemia in which your body destroys red blood cells faster than it produces them, often due to certain blood diseases or autoimmune disorders
  • Inflammation, such as from rheumatoid arthritis, celiac disease, connective tissue disorders or inflammatory bowel disease
  • Major surgery
  • Pancreatitis
  • Trauma

Medications that can cause reactive thrombocytosis include:

  • Epinephrine (Adrenalin Chloride, EpiPen)
  • Tretinoin
  • Vincristine
Sep. 25, 2012