What Is MCV in a Blood Test?

MCV stands for Mean Corpuscular Volume. It measures the average size of your red blood cells. Red blood cell size helps classify anemias and can signal vitamin deficiencies, chronic disease, or bone marrow disorders.

Normal Ranges

• Adult normal range: 80–100 fL (femtoliters)
• Microcytosis (MCV below 80 fL): small red blood cells — characteristically seen in iron deficiency anemia, thalassemia, and sometimes anemia of chronic disease.
• Macrocytosis (MCV above 100 fL): large red blood cells — associated with vitamin B12 or folate deficiency, alcohol use, liver disease, hypothyroidism, or certain medications.

What Causes High MCV?

• Vitamin B12 deficiency — impaired DNA synthesis produces oversized cells
• Folate deficiency — similar mechanism to B12
• Alcohol use — direct toxic effect on bone marrow
• Liver disease — altered lipid metabolism affects cell membranes
• Certain medications — methotrexate, phenytoin, zidovudine

What Causes Low MCV?

• Iron deficiency anemia — insufficient hemoglobin production yields smaller cells
• Thalassemia trait — genetic defect in globin chain production
• Anemia of chronic disease — inflammation-driven suppression of erythropoiesis