Symptoms of a high platelet count include headache, bleeding, feeling weak, and numbness in the hands or feet, states Healthgrades. Blood-clotting symptoms, including nausea, seizures, dizziness, difficulty breathing and cognitive problems, may occur along with a high platelet level. High numbers of platelets may cause brain damage (including stroke) or blood clots.
Bloody nose, mouth bleeds, bleeding gums, bloody stool and bruising easily may indicate that a person has a high platelet count, according to Healthgrades. Pain in the jaw, neck or abdomen and extreme pain in the arms or legs are other symptoms that may occur along with thrombocytosis. Feeling faint, lightheadedness, tingling of the hands or feet, vision problems and chest pain may signify that a person has excess platelets, according to Mayo Clinic.
Difficulty with speech, difficulty breathing and headache that does not get better are potentially life-threatening symptoms of too many platelets; a person with these symptoms should seek immediate medical attention. Causes of high blood platelets include anemia, certain infections, cancer, chemotherapy and certain medications. Polycythemia vera, a bone marrow disorder in which there is too much production of blood cells; surgical removal of the spleen; inflammatory disorders, including Kawasaki disease; and myelofibrosis can lead to the problem as well. Blood tests should be done before treatment to help determine the cause of the problem, advises Mayo Clinic.