Which lab value is used to monitor the response to epoetin alfa therapy?

• A. Hematocrit
• B. Serum phosphate
• C. Serum potassium
• D. Serum calcium

Answer: (A)

Hematocrit is used to monitor the response to epoetin alfa therapy. Epoetin alfa stimulates the bone marrow to produce more red blood cells, so the proportion of blood made up by these cells increases as the treatment takes effect. Hematocrit (the percentage of red blood cells in whole blood) directly reflects this change in red cell mass and helps clinicians gauge whether the dose is achieving the desired improvement without pushing values too high.

While hemoglobin is also a common monitor, the other options—serum phosphate, potassium, and calcium—are measures of mineral or electrolyte status and do not indicate how well red blood cell production is responding to therapy. Monitoring aims to raise the red cell mass to a safe, target range while avoiding excessive hematocrit that could increase risks such as thrombosis or hypertension.