MCV stands for mean corpuscular volume — the average size of your red blood cells. It is reported on every CBC and is one of the most useful numbers for working out why someone is anemic. See typical values on our MCV guide.
Low MCV (microcytic)
Small red cells most often mean iron deficiency, especially when hemoglobin is also low. Confirm with ferritin. A low MCV can also indicate thalassemia trait, which is common in South Asian, Mediterranean and Middle Eastern populations.
High MCV (macrocytic)
Large red cells point toward vitamin B12 or folate deficiency. Other causes include alcohol use, an underactive thyroid (TSH) and liver disease.
Normal MCV with anemia
If your MCV is normal but hemoglobin is low, the anemia is called normocytic — often seen with chronic disease, kidney problems or recent blood loss.
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This article is for general education only and is not medical advice. Reference ranges vary between laboratories — always read your result against the range on your own report and discuss it with your doctor.