Mean Corpuscular Volume (MCV)

Synonyms: MCV, mean cell volume, mean corpuscular volume

What is MCV?

To ensure the ability to transport oxygen through the body, red blood cells should have several characteristics, including their volume. Too large red blood cells (erythrocytes) are not able to pass through the smallest capillaries, and if the red blood cells are too small, they can’t carry enough hemoglobin. In both cases, the risk of hypoxia (oxygen starvation) increases which can have negative consequences for the whole body. Red blood cell (RBC) indices help estimate the size of red blood cells and their hemoglobin content. RBC indices characterize the cells, rather than their quantity, as a result they are relatively stable parameters. The mean corpuscular volume (MCV) is one of the red blood cell indices.

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The MCV shows a more accurate size of red blood cells than when they are studied with a regular microscope. Nevertheless, the MCV is not a reliable marker in case of a high number of red blood cells with abnormal shape.

The MCV is used primarily to determine the type of anemia. Depending on the values of MCV, anemia can be divided into microcytic, normocytic and macrocytic. Microcytic anemia can be due to iron deficiency, anemia of chronic disease, thalassemia. When your body lacks folic acid or vitamin B12, macrocytic anemia develops. Normocytic anemia includes hemolytic anemia, hemoglobinopathy, aplastic anemia, and anemia after bleeding.

The MCV can be calculated using the hematocrit level (HCT) and the number of red blood cells (RBC) as follows:

MCV (fL) = HCT (%) / RBC х 10

MCV in Pregnancy

Pregnancy is accompanied by numerous changes in the body of a woman, aimed at ensuring the normal development of the fetus. During pregnancy, the volume of circulating blood in the mother’s body increases. The increase is mainly due to plasma volume (about 40%), while the red blood cell (RBC) mass increases by about 15%, resulting in physiological (relative) anemia. The hemoglobin level and the hematocrit value physiologically decrease. But relative anemia has no effect on MCV.

MCV Units

Units of measurement that may be used for MCV test include:

• femtoliter (fL)
• cubic micrometer (μm³)

MCV Reference Range

Normal MCV values may vary slightly among different laboratories.

The normal range of MCV in adults is 80-95 fL.

Newborns have higher level of MCV in the blood due to young red blood cells (reticulocytes). Reticulocytes are about 8% larger than mature cells, so the MCV is higher.

The MCV reference range in newborns is 96-108 fL. Reference values vary based upon child's age.

Normal MCV

A normal MCV level indicates a normal average red blood cell size. However, if the RBCs are normal in size, you may still have anemia when your red blood cell count is low. This condition is called normocytic anemia.

The major causes of normocytic anemia are as follows:

• Decreased red blood cell production (aplastic anemia, anemia of chronic diseases)
• Increased destruction or loss of red blood cells (acute blood loss, hemolysis)
• Excessive increase in plasma volume (pregnancy, hyperhydration)

High MCV

An increase in MCV level is called "macrocytosis." The amount of hemoglobin increases in proportion to the increase in cell size. An increase in MCV together with reduced hemoglobin (HGB) or hematocrit (HCT) is called macrocytic anemia. This condition implies that the body contains too large red blood cells and an insufficient number of red blood cells of a normal size. Macrocytic anemia is not a separate disease, but a symptom of several diseases or nutritional problems.

Macrocytic anemia can be divided into two main types:

• Megaloblastic anemia
• Non-megaloblastic anemia

Most macrocytic anemias are megaloblastic. They are caused by impaired DNA synthesis during the production of red blood cells.

The causes of megaloblastic macrocytic anemia are as follows:

• Lack of folic acid or vitamin B12 (the most common cause)
• Some medications (chemotherapy drugs, birth control, antiretroviral drugs used for people with HIV)

Non-megaloblastic macrocytic anemia can be caused by various factors:

• Alcohol consumption
• Liver disease
• Hypothyroidism

Macrocytosis without anemia often are not of serious clinical significance. Elevated MCV is normal in infants. In late pregnancy, a short-term moderate increase in MCV may also be noted.

Low MCV

A decreased MCV, that is, when red blood cells are smaller than they should be, is called "microcytosis." With microcytic anemia, the body contains little oxygen because the red blood cells are too few or the red blood cells do not contain enough hemoglobin.

Causes of low MCV:

• Iron deficiency anemia is the most common type of microcytic anemia that most often occurs due to inadequate intake of iron with food, heavy menstrual bleeding, or gastrointestinal bleeding.
• Thalassemia (a hereditary blood disease).
• Chronic diseases (kidney disease, diabetes, heart failure, inflammatory bowel disease, rheumatoid arthritis, infectious diseases, some types of cancer).
• Lead poisoning.
• Copper deficiency.
• Excess zinc.
• Alcohol and drug use.