What Are the Causes of Elevated Platelet Count?

Platelets are also called thrombocytes. They are small fragments of large bone marrow cells (megakaryocytes) that clump together to assist in the clotting of blood. Thrombocytes are smaller than red and white blood cells. A normal platelet count is about 150,000 to 400,000 per milliliter of blood. Thrombocytosis describes an elevated platelet count above 400,000 per ml. There are several conditions that could cause an elevated platelet count such as anemia.

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According to the Mayo Clinic, thrombocytosis (too many platelets in the blood) is a disorder also known as reactive thrombocytosis that may affect children and adults 2. An elevated platelet count is an indication that there is an underlying condition that is causing the disorder. The test to measure how many platelets are in your blood is called a platelet count.


Platelets or thrombocytes are made in the bone marrow; these tiny fragments are then released into the blood. Platelets are activated as the first responders to protect damaged cells when there is bodily injury to the blood vessels or tissues. Their sticky composition starts the clotting process to prevent hemorrhage. Too many platelets in the blood can cause blood clots that may cause strokes or heart attacks. Defective platelets may cause hemorrhaging, or unstoppable bleeding.


According to Netdoctor.com, the two basic processes involved in a high platelet count are: The cell within the bone marrow produces more platelets, or less platelet matter is removed from the blood by the spleen. The latter only occurs after a splenectomy (an operation to remove the spleen) is done. Increased platelet production is usually the cause of an elevated platelet count.

Other Causes

The other causes of an elevated platelet count may include anemia (too few red blood cells), certain types of cancer and polycythemia vera (too many re blood cells.) An elevated platelet count could also be casued by early chronic myelogenous leukemia, a malignant disorder that involves abnormal accumulation of white cells in the bone marrow and the blood stream, or by a recent splenectomy.

Additional Causes

These include primary thrombocytosis; this is a high platelet count due to a blood disorder affecting the make up of the blood itself. In addition, reactive thrombocytosis may occur, which is an elevated platelet count that may be due to an infection, an operation or an acute blood loss. Reactive thrombocytosis may also be caused by inflammation due to such causes as rheumatoid arthritis, or to an inflammatory bowel condition.


Some signs and symptom of an elevated platelet count are: Bleeding from the nose mouth or rectum or unexplained bruising and heavy or prolonged menstrual cycle. The treatment of thrombocytosis depends on the source of the condition. Once the cause of the problem is identified, treated and resolved, the platelet count returns to normal.