After donation, your body goes to work regenerating the lost blood. Your plasma recovers the quickest, in about 24 hours (9). The Red Cross recommends no strenuous exercise during this period until your “fluid” or plasma normalizes (9). Platelets restore next, within a 72-hour period (13). The oxygen carriers or RBCs – unfortunately for athletes – are the slowest to regenerate, taking four to six weeks to fully rebound (9).

The lag in RBC recovery is an obvious indicator that an athlete’s endurance performance will suffer until pre-donation levels are restored. Several studies have reported significant drops in performance measures from 24 hours to two days post-donation in active young adults, including VO2 max, work rate (4,5,6,7), and time to exhaustion (5). Dellweg et al. reported a 9% decrease in VO2max, and a 13% drop in maximal work rate following a 500-ml whole blood donation (6).