Mean Corpuscular Volume - MCV

MCV Shows the Size of Red Blood Cells and Causes of Anemia

Red blood cells. Credit: Pasiek / Getty Images

Mean corpuscular volume (MCV) Definition

Mean corpuscular volume (MCV) is a blood test that measures the average red blood cell volume, in other words, its size. MCV is part of a Complete Blood Count (CBC) test, and you will see it reported there along with other measures your red cells, white cells, and platelets.

  • The normal range for MCV in adults is 80-100 fL/red cell. This is called normocytic.
  • High MCV: over 100, called macrocytic, the red cells are larger than normal.
  • Low MCV: below 80, called microcytic, the red cells are smaller than normal.

What Does the MCV - Mean Corpuscular Volume  Mean?

You can have a high or low MCV without having an obvious disease process and without being anemic, sometimes this is just a variation. But a high or low MCV is often seen with anemia when your blood has a reduced red blood cell count and/or hemoglobin. In this case, the MCV is a useful value to determine what is causing the anemia.

A high MCV along with anemia is called macrocytic anemia. It can have a variety of causes including alcoholism, liver disease, and deficiencies of vitamin B12 and folic acid (folate). During cancer treatment, you may develop a macrocytic anemia during chemotherapy. This happens because the red cell production in the marrow is out of sync, and the red cells grow larger and larger before they are finally released into the bloodstream.

A low MCV along with anemia is called microcytic anemia.

It is most commonly caused by iron deficiency, as the red cells are smaller than normal because of the lack of hemoglobin. Ongoing blood loss, such as what might occur with tumors in the colon and other parts of the gastrointestinal tract, can cause the low iron levels that lead to microcytic anemia.

A low MCV can be a clue that you have had ongoing, silent blood loss which you may not have been aware of, which is an important clue for your doctor to explore. It can also be seen in lead poisoning, inflammation, and thalassemia.

A normal MCV along with anemia is called normocytic anemia. You may develop this due to long-term disease or having a tumor. Other causes include sudden blood loss, a blood infection, or kidney failure reducing the erythropoietin hormone.

How the MCV Test is Performed - A Check on Mix-Ups

The CBC is performed on the anticoagulated blood sample usually drawn in a purple top tube and analyzed in a Coulter counter. Each red cell passes through an aperture, and its size is measured to give the average result. Often a differential is ordered with a CBC, and the laboratory technologists will make a slide and examine it under the microscope. They assess the size of your red cells visually and use this to confirm what was measured by the Coulter counter.

Your MCV should not change significantly over the course of a few days, as it takes weeks for conditions in your body to result in a change in your red blood cell size.

However, it can change if you have had a transfusion as the donor blood cells may be a different size from your own. The lab technologists will immediately suspect something was wrong with your sample if they see a change in your MCV and will inform your doctor. If you haven't had a transfusion, a repeat test is needed. The sample may have been mislabeled or mishandled.


Todd Gertsten, MD. "RBC indices," Medline Plus, U.S. National Library of Medicine, Updated 2/24/2014.

Michele Van Vranken, MD, "Evaluation of Microcytosis," Am Fam Physician. 2010 Nov 1;82(9):1117-1122.

Florence Aslinia, MD, Joseph J. Mazza, MD, MACP, and Steven H. Yale, MD, FACP. "Megaloblastic Anemia and Other Causes of Macrocytosis," Clin Med Res. 2006 Sep; 4(3): 236–241.

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