Iron recovery dynamics after whole blood donation and the effect of low‐dose iron supplementation in Japanese donors

Abstract Background and Objectives Iron deficiency (ID) poses a non‐negligible risk for blood donors, yet longitudinal data on iron status and whether low‐dose iron‐containing supplements improve ID among Japanese donors are scarce. This study aimed to elucidate these issues. Materials and Methods Sixty‐six healthy Japanese donated 400 mL of whole blood (WB) and underwent scheduled blood samplings. Fourteen participants discontinued follow‐up; 52 donors completed the second 400 mL WB donation at Week 48. Participants were subsequently provided supplements containing 6 mg/day of ferric citrate for 12 weeks, with continued monitoring through Week 48; the total duration of participation in the study was 96 weeks. Haematological data were analysed using a linear mixed‐effects model. Results In men, serum ferritin (sFer) declined from 116.2 ng/mL (95% confidence interval 95% CI: 88.0–144) to 83.7 ng/mL (55.5–112) at Week 4 and returned to baseline by Week 36. In women, sFer decreased from 29.2 ng/mL (21.74–36.7) to 16.6 ng/mL (9.16–24.1) at Week 4 and returned to baseline at Week 24. Recovery of sFer was slower than that of haemoglobin (Hb) in both sexes. Iron supplementation did not affect the recovery of Hb and sFer in men and Hb in women, whereas women showed a significant increase in sFer at Week 16. Conclusion Although Hb recovered quickly after 400 mL WB donation, replenishment of iron stores took longer. Low‐dose iron supplementation facilitated the recovery of iron stores in women. These findings highlight the need for monitoring iron status and may inform strategies to support donor safety and maintain adequate blood supply.