Bone marrow — spongy tissue inside your bones — contains stem cells that can become red blood cells, white blood cells or platelets (thrombocytes). Platelets stick together, helping blood to form a clot that stops 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. In essential thrombocythemia, there is a much higher risk of clotting or bleeding complications. Therefore, 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
  • Coronary artery bypass
  • Infections, including tuberculosis
  • Iron deficiency
  • Vitamin deficiency
  • 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
  • Burns
  • Exercise

Medications that can cause reactive thrombocytosis include:

  • Epinephrine (AUVI-Q, EpiPen, others)
  • Tretinoin (Retin-A, Renova, others)
  • Vincristine Sulfate (Marqibo Kit)
  • Heparin sodium
July 10, 2015