Thrombocytosis is a disorder in which your body produces too many platelets (thrombocytes), which play an important role in blood clotting. The disorder is called reactive thrombocytosis or secondary thrombocythemia when it's caused by an underlying condition, such as an infection.

Thrombocytosis (throm-boe-sie-TOE-sis) may also, less commonly, be caused by a blood and bone marrow disease. When caused by a bone marrow disorder, thrombocytosis is called autonomous, primary or essential thrombocytosis, or essential thrombocythemia.

Your doctor may detect thrombocytosis in routine blood test results that show a high platelet level. If your blood test indicates thrombocytosis, it's important to determine whether it's reactive thrombocytosis or if you have essential thrombocythemia, which is more likely to cause blood clots.

July 10, 2015