What does it mean when your platelet count is high?

Could be reactive: Many secondary cause including infection or underlying inflammatory conditions. Also bleeding, iron deficiency or people whose spleens have been removed. Sometimes, more associated with older populations conditions associated with primary bone marrow disorders called myleoproliferative disease can be associated with increase platelets.

Many causes: Most common one is iron deficiency, chronic inflammation could cause it as well as infection the most important one is essential thrombosis which could increase risk of blood clots and strokes.