Iron parameters and circulating non–transferrin-bound iron levels increase after transfusions of older RBCs in healthy volunteers. (A) The mean ± SEM and (B) individual levels of serum iron; (C) mean ± SEM and (D) individual levels of transferrin saturation; (E) increase in ferritin compared with baseline levels; and (F) increase in plasma non–transferrin-bound iron compared with baseline levels from before transfusion to 72 hours after transfusion of fresh and older RBCs. Vertical arrows indicate pretransfusion time points; and dotted lines, the reference range (the reference range for change in ferritin and non–transferrin-bound iron is 0 by definition). The P values are as specified in the figure comparing the paired area under the curve of the mean of the outcome parameter for the N = 14 volunteers from 0 to 24 hours after the fresh and older RBC transfusions.