What Causes High Blood Platelets?

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Better Medicine states that high platelet production is categorized as either primary thrombocythemia, which occurs for reasons unknown, or secondary thrombocytosis, which is caused by another condition, such as infection, anemia or cancer. A high platelet level means that the blood has an abnormal number of platelets.

Platelets are tiny blood cell fragments made in bone marrow that help in blood clotting, according to Better Medicine. A healthy person normally has 150,000 to 450,000 platelets in every microliter of blood. Primary thrombocythemia is a condition wherein the bone marrow produces excessive platelets. In this case, high platelet levels occur as an independent condition without any other cause. Primary thrombocythemia can be inherited. In secondary thrombocytosis, high platelet production results from another condition. There are many diseases and conditions that lead to high platelets, including anemia, blood loss, chemotherapy, cancer, infection and inflammatory disorders.

Better Medicine notes that high platelet levels that occur due to serious diseases can result in severe complications and permanent damage, including bleeding, blood clots and brain damage. When caused by an underlying disease, high platelet levels are accompanied by other symptoms, such as weakness and bleeding. However, some people do not experience any symptoms, and high platelet levels are detected only by routine blood tests.