Mean corpuscular volume (MCV) represents the:

• A. Number of red blood cells
• B. Shape of the cell
• C. Average volume or size of red blood cells
• D. Hematocrit

Answer: (C)

Mean corpuscular volume tells you the average size of individual red blood cells. It’s used to classify anemia as microcytic, normocytic, or macrocytic, guiding further workup. MCV is calculated from hematocrit and red blood cell count (roughly MCV = hematocrit × 10 / RBC), and is expressed in femtoliters. Normal range is about 80–100 fL. A low MCV means smaller-than-normal cells, as seen in iron deficiency; a high MCV means larger-than-normal cells, as in B12 or folate deficiency or reticulocytosis. It does not measure the number of red blood cells (that’s RBC count) or the overall hematocrit, which is the proportion of blood volume occupied by red cells. It also is not a direct measure of cell shape—that’s assessed by morphology on a smear.