biostudies-literatureMeulenbeld AStichting Sanquin BloedvoorzieningSanquin Blood Supply FoundationAABB Foundation1096-1103https://www.ebi.ac.uk/biostudies/studies/S-EPMC12436240biostudies-literatureUnknown207(3)Many blood establishments worldwide monitor serum ferritin alongside mandatory haemoglobin (Hb) screening to better protect donors from iron deficiency and anaemia. However, the relationship between ferritin and Hb, and the ferritin level that indicates iron deficiency, remains unclear. Whole blood donation results in significant iron loss, and repeated donations can deplete iron stores. This study analysed over 1 million whole-blood donations from four countries to explore the association between Hb change and ferritin levels. Hb change was defined relative to a donor's initial Hb level. A consistent two-phase relationship emerged: At low ferritin levels, Hb change is linearly associated with log ferritin; above a certain threshold, this association disappears as donors recover their refeBritish journal of haematologyBlood donor populations reveal a clear association between ferritin and change in haemoglobin levels.PMC12436240PPOC23‐09/L2753PPOC23-09/L2753PPOC21-10/L2590PPOC21‐10/L2590Qi Hvan den Hurk KPothast MRMeulenbeld ABrits TArvas MLi WAllara EMatlung HLTurkulainen EVDi Angelantonio ERussell WAJanssen MPINTERVAL Trial GroupSwanevelder RPaalvast YSwinkels DWfalseBlood donor populations reveal a clear association between ferritin and change in haemoglobin levels.Many blood establishments worldwide monitor serum ferritin alongside mandatory haemoglobin (Hb) screening to better protect donors from iron deficiency and anaemia. However, the relationship between ferritin and Hb, and the ferritin level that indicates iron deficiency, remains unclear. Whole blood donation results in significant iron loss, and repeated donations can deplete iron stores. This study analysed over 1 million whole-blood donations from four countries to explore the association between Hb change and ferritin levels. Hb change was defined relative to a donor's initial Hb level. A consistent two-phase relationship emerged: At low ferritin levels, Hb change is linearly associated with log ferritin; above a certain threshold, this association disappears as donors recover their refe2025-01-01T00:00:00Z2025 Sep2026-06-03T02:54:42.654Z2026-04-23T03:13:12.569ZS-EPMC124362404077090510.1111/bjh.70066