We investigated whether intravenous
iron supplementation improves
fatigue and general health in non-anemic repeat adult blood donors with
iron deficiency (ferritin ≤ 50 µg/L). Of 1,487 potentially eligible participants, 203 were randomly assigned to a single intravenous dose of 800 mg
iron-carboxymaltose and 202 to placebo; 393 participants completed the trial. At 6 to 8 weeks after intervention, self-rated mean
fatigue scores (numeric rating scale from 1-10, primary outcome) were 3.9 ± 1.8 in the
iron supplementation group and 4.0 ± 2.2 in the placebo group, showing no group difference (p = 0.819). Pre-specified subgroup analyses of gender, ferritin < 25 µg/L and fatigue ≥ 4 points, as well as exploratory analyses of lower
ferritin cut-offs did not reveal any between-group differences. In terms of secondary outcomes, the mean differences were 114.2 µg/L for
ferritin (95% CI 103.1-125.3) and 5.7 g/L for
hemoglobin (95% CI 4.3-7.2) with significantly higher values in the
iron supplementation group. No group differences were observed for different measures of general well-being and other clinical and safety outcomes. Intravenous
iron supplementation compared with placebo resulted in increase of
ferritin and
hemoglobin levels in repeat blood donors with low
iron stores, yet had no effect on
fatigue and general well-being.