Which lab finding would most directly indicate bone marrow is actively producing red blood cells in a patient with anemia?

• A. Decreased Reticulocytes
• B. Elevated Bilirubin
• C. Elevated Reticulocytes
• D. Normal Hemoglobin

Answer: (C)

The main idea is that reticulocytes reveal how actively the bone marrow is making red blood cells. Reticulocytes are the immature RBCs released into circulation as the marrow ramps up production. In anemia, a higher reticulocyte count shows the marrow is actively compensating by producing more RBCs, so this is the best indicator of marrow activity.

Elevated bilirubin reflects increased breakdown of red cells, not how much the marrow is producing. Normal hemoglobin by itself doesn’t tell you whether the marrow is actively producing RBCs or not. So the elevated reticulocytes specifically point to active production by the bone marrow.