Mean Corpuscular Volume (MCV) measures the average size of red blood cells, with a normal range of ~80–100 fL. It is primarily used to classify types of anemia.

Low MCV suggests smaller red cells, often seen in iron deficiency or thalassemia, while high MCV indicates larger cells, commonly associated with B12 or folate deficiency, alcohol use, or certain medications. In otherwise healthy individuals, mild isolated changes can reflect nutrition or lifestyle factors, but persistent abnormalities warrant further evaluation.