How often can a person donate blood?

Whole blood donors may give once every three months in order to allow plenty of time to replenish their red cells. Apheresis platelet donors can donate more frequently, as much as every seven days, up to 24 times per year, because the platelet and plasma components are replaced in the body more quickly than red cells. Blood volume or plasma is replaced within 24 hours. Red cells need about 4-5 weeks for complete replacement.