Platelet volume is the volume of all platelets in the peripheral blood, as a % of the whole blood volume. There are three types of high platelet volume. The first one is the relative high platelet volume caused by hematoconcentration. It is common when the body is dehydrated such as severe vomiting and diarrhea. As long as active rehydration is given, such as saline, Ringer’s solution, etc., after the blood volume is expanded, the elevated platelet volume will gradually drop to the normal range and has no obvious effect on the human body. The second type of platelet volume increase is caused by the increase in platelet count. If the increase in platelet count is caused by inflammation, infection, hemolysis, surgery, etc., this is also called reactive platelet count increase, generally after treatment of the original disease, the platelet count will gradually return to normal, and the hematocrit will gradually return to normal. The third type is the high hematocrit caused by primary thrombocytosis. At this time, it is necessary to apply platelet separator to separate out the excessive platelets or apply hydroxyurea to lower the platelets, so that the elevated platelet count will also gradually decrease to normal.