Mean corpuscular volume

MCV is calculated as (Hematocrit/RBC count) × 10, and is a key first step in the diagnostic algorithm for anemia. Microcytic anemia (MCV <80 fL) is most commonly caused by iron deficiency, thalassemia, anemia of chronic disease, sideroblastic anemia, or lead poisoning (mnemonic: TAILS). Normocytic anemia (MCV 80-100 fL) can be due to acute blood loss, hemolysis, chronic disease, aplastic anemia, or bone marrow infiltration; further workup often includes reticulocyte count to distinguish hypoproliferative from hyperproliferative causes. Macrocytic anemia (MCV >100 fL) is divided into megaloblastic (due to vitamin B12 or folate deficiency, impaired DNA synthesis leading to hypersegmented neutrophils) and non-megaloblastic causes (alcoholism, liver disease, hypothyroidism, myelodysplastic syndrome, reticulocytosis). MCV should always be interpreted alongside other RBC indices such as MCH (mean corpuscular hemoglobin), MCHC (mean corpuscular hemoglobin concentration), and RDW (red cell distribution width) for a complete picture. For example, an elevated RDW suggests anisocytosis (variation in RBC size), which is characteristic of iron deficiency anemia but typically normal in thalassemia trait, helping to distinguish these two microcytic anemias. Clinically, MCV is part of the complete blood count (CBC) and is essential for guiding further diagnostic testing (e.g., iron studies, vitamin B12/folate levels, hemoglobin electrophoresis) and determining the underlying etiology of anemia, which directly impacts treatment decisions.