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By Mayo Clinic staffReactive thrombocytosis is rarely associated with symptoms. However, a high platelet count can be an indication of a serious bone marrow condition (also known as primary thrombocytosis or thrombocythemia), rather than of an underlying condition such as an infection. Thrombocythemia may put you at risk of developing blood clots, some of which can be life-threatening.
When to see a doctor
Because thrombocytosis is not likely to be associated with symptoms, you won't know you have the condition unless a routine blood test reveals a high platelet count. Getting those test results will necessitate further consultation with your doctor.