According to the Red Cross, platelets, which are found in the blood, have a life span of five to nine days. The spleen eliminates any platelets that are old or that have stopped working properly. The University of Oklahoma states that bone marrow produces new platelets.
Platelets are tiny but numerous, the Red Cross indicates. One microliter of blood normally has 150,000 to 400,000 platelets. However, they make up less than one percent of blood's volume. Unlike full red and white blood cells, platelets are only pieces of cells. Their function is to minimize the loss of blood. Platelets form clumps to plug holes, which stops blood flow.