I donate platelets regularly to the American Red Cross. Platelet donations take much longer than whole blood (2.5 hours versus 15-30 minutes), but for my blood type (AB+), platelets are much more valuable, as patients with nearly any blood type can receive AB+ platelets. (For whole blood, only AB+ patients can receive AB+ donations.) In addition, the Red Cross facility in Washington, DC is stocked with a library of movies to watch while donors are immobilized on the beds, so it’s been a great opportunity to catch up on the hits I’ve missed from the past 50 years.

The process takes longer because the platelets need to be sorted out from your blood. In order to have a sizeable amount of platelets, they need to take a lot of blood out of your body – more than is safe to not put back. An apheresis machine, which sits behind the bed, sucks blood from one arm, filters platelets (and sometimes plasma) from the rest of your blood, and returns the rest of your blood (white blood cells, red blood cells, plasma) back to your body in another tube. I think the apheresis machine separates blood components using a centrifuge, but I’m not certain.

Platelets are most commonly used to assist people fighting cancer. Chemotherapy often kills platelets, so platelet donations are required to ensure proper healing while patients recover from the treatment.