Background:Iron-deficiency anemia is an important limiting factor to a sustainable supply of blood units, especially in low- and middle-income countries. Blood transfusion practice in Nigeria is poorly developed and structured with paucity of voluntary nonremunerated blood donors and high rate of donor deferrals resulting from low hemoglobin (Hb) levels.Aims:This study aimed to assess the effect of daily supplementation of iron using Ranferon-12 on Hb level, red blood cell (RBC) indices, iron level, ferritin level, and Hb recovery in blood donors in Nigeria.Methodology:This longitudinal study was conducted at a tertiary hospital blood transfusion center from March to July 2020. Blood samples of regular donors were collected at three points in the study for the measurement of Hb and hematocrit (HCT); RBC indices including mean cell volume (MCV), mean cell hemoglobin (MCH), and Mean cell haemoglobin concentration (MCHC); and iron stores including serum iron, serum ferritin, and serum transferrin. The first point was at recruitment before donation of one unit of blood; the second point after the blood donation; and the third point at 6 weeks post blood donation. Following donation, participants were placed on Ranferon capsules (iron fumarate - 100 mg elemental iron) and 100 mg of tablet Vitamin C, for 6 weeks.Results:There was a moderate significant positive correlation between administration of Ranferon and change in the values of HCT, MCV, MCH, red cell distribution width, ferritin, and transferring (P< 0.05). Percentage recovery of Hb, red cell indices, and iron stores parameters after 6 weeks of daily Ranferon ranged between 89% and 100%.Conclusion:Iron supplementation using Ranferon capsule daily for 6 weeks enhances recovery of Hb, red cell indices, and iron stores with attainment of benchmark Hb levels for donation.