A high platelet count indicates too many of the small cells (platelets) that help form blood clots. This can cause dangerous clots and bleeding. Also called thrombocytosis or thrombocythemia, ...

A high platelet count, or thrombocytosis, is diagnosed when platelet levels are greater than 450,000 platelets per microliter of blood. A high platelet count can lead to symptoms that range from ...

"We've long known that ovarian cancer patients often have markedly increased platelet counts but we haven't known why this happens or understood its relevance, if any, to disease progression," said ...