Red blood cells last up to 42 days in a fridge, but platelets expire in just 5 days.

Platelets are small cell fragments in our blood that form clots to stop bleeding. Unlike red blood cells, which are preserved by refrigeration at 1 to 6 degrees Celsius, platelets lose their ability to function if they get too cold. Cold temperatures trigger a structural change in the platelet cytoskeleton, causing them to be rapidly cleared by the liver once transfused.Because they must be stored at a room temperature of 20 to 24 degrees Celsius, they are highly susceptible to bacterial growth. This risk is the primary reason the U.S. Food and Drug Administration (FDA) limits their shelf life to just five days. To prevent the platelets from clumping and to ensure oxygen exchange, they are kept on machines called agitators that provide constant gentle rocking.The demand for platelets is immense, particularly for chemotherapy patients whose bone marrow cannot produce enough of them. According to the American Red Cross, about 2 million units of platelets are transfused annually in the United States. Because of the 120-hour expiration window, blood centers must maintain a continuous stream of donors to avoid critical shortages during holidays or disasters.