In plasmapheresis, whole blood is drawn through a needle placed in an arm vein. The blood flows into a cell separator machine, where it is spun to separate the plasma from the blood cells. The plasma is collected in a plastic bag in the machine, while the rest of the blood is returned to the donor through the needle in the arm. During the procedure, the donor is given a blood thinner called citrate to prevent the blood from clotting while it is in the cell separator machine. The procedure lasts from 60 to 90 minutes. Only a small fraction of the body's total plasma is removed, and it is quickly replaced by the body with no long-term health effects. Participants may be requested to donate plasma as often as every 3 to 4 days or as infrequently as once a month for a maximum of six donations.