Platelets are colorless cell fragments called thrombocytes. Their main function is to stick to the lining of blood vessels and stop bleeding.
The process of clotting begins if one of your blood vessels gets damaged. The vessel sends out signals that are picked up by platelets. The platelets then rush to the site of damage and form a plug, or clot, to repair the damage.
Many lifesaving medical treatments for patients require platelet transfusions: Cancer patients, those receiving organ or bone marrow transplants, victims of traumatic injuries, and patients undergoing open heart surgery. Platelets must be transfused within just 5 days after donation - so there is a constant, often critical need for new and current donors to give to keep up with hospital demand.