RBC levels decline to approximately what range by 2-3 months of age?

• A. 4-6 g/dL
• B. 9-11 g/dL
• C. 12-14 g/dL
• D. 15-17 g/dL

Answer: (B)

A healthy infant undergoes a physiological drop in hemoglobin after birth, known as physiologic anemia of infancy. At birth, Hb is high due to fetal hemoglobin and a large red cell mass. After birth, oxygen levels improve, which reduces erythropoietin production, and the blood becomes more diluted as plasma volume expands. Additionally, newborn red cells have a shorter lifespan, so turnover increases. All of this combines to lower the hemoglobin concentration to about 9–11 g/dL by roughly 2–3 months of age. This nadir is expected and normal. Values much lower than this would raise concern for pathology, whereas higher values reflect the transitional neonatal Hb that has not yet reached this nadir.