What does having a high blood platelet count mean?

Thrombocytosis... ...Is the clinical term for a platelet count > 450k. This is subclassified as primary (essential) vs. Secondary: the former is due to unexplained production of platelets, the latter is most often due to chronic infections or inflammation (crohn's dz), anemia, cancer, a rxn to a medication, or following the surgical removal of the spleen. For more info check www.Thrombocytosis.Net.
Thrombocytosis. The most common cause of an elevated platelet count is iron deficiency anemia. Some people are born with thrombocytosis. Other causes include chronic infection or inflammation, metastatic cancer, and essential thrombocythemia, a bone marrow disorder which causes excessive production of platelets. For the correct diagnosis and treatment, you will need to see a hematologist.