Why does MCV decrease?

Mean corpuscular volume (MCV) can decrease due to various factors, primarily related to conditions that result in smaller red blood cells. Common causes include iron deficiency anemia, thalassemia, and certain chronic diseases. These conditions affect hemoglobin synthesis or red blood cell production, leading to microcytic anemia, which is characterized by low MCV values. Additionally, chronic blood loss or inadequate dietary intake of essential nutrients can also contribute to a decrease in MCV.