Chronic hypoxia at high altitude induces which hematologic adaptation?

• A. Decreased hematocrit
• B. Increased hematocrit
• C. Increased hemoglobin concentration with unchanged hematocrit
• D. Decreased RBC count

Answer: (B)

Chronic hypoxia at high altitude stimulates the kidneys to release erythropoietin, which drives increased production of red blood cells. This expansion of red cell mass raises hematocrit, boosting the blood’s oxygen-carrying capacity to offset the lower environmental oxygen. Thus the body adapts by increasing hematocrit (and hemoglobin concentration) to improve oxygen delivery. The other options describe scenarios that would worsen oxygen transport or fail to enhance oxygen carrying capacity.