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This is measurement related to red blood cells (RBCs) size and is part of the Complete Blood Count (CBC), a frequently requested test ordered for a variety of health conditions.

Mean corpuscular volume (MCV) is a calculation of the RBCs' average size. The MCV is increased if RBCs are larger than normal (macrocytic), for example in anemia caused by vitamin B12 deficiency. When the MCV is low RBCs are smaller than normal (microcytic) as is found in iron deficiency anemia or thalassemia.
If anemia is present, MCV measurement allows classification as microcytic anemia (MCV below normal range), normocytic anemia (MCV within normal range) or macrocytic anemia (MCV above normal range).

The test ordered to measure the average size of the individual erythrocytes in femtoliters. MCV level is a result of dividing the hematocrit value by the RBC count in millions/microliters of the blood. The resulted value is then multiplied by 10. Hematocrit is measured by a test that calculates the percentage of blood volume taken up by the red blood cells. Just like the other components of the complete blood count test, MCV is performed to detect if the patient is suffering from any ailment or blood diseases. If MCV is abnormal, it indicates that patient may be suffering from an asymptomatic ailment.

Test Results

In presence of hemolytic anaemia, presence of reticulocytes can increase MCV. In pernicious anemia (macrocytic), MCV can range up to 150 femtolitres. An elevated MCV is also associated with alcoholism (as are an elevated GGT and a ratio of AST:ALT of 2:1). Vitamin B12 and/or Folic Acid deficiency has also been associated with macrocytic anemia (high MCV numbers).

The most common causes of microcytic anemia are iron deficiency (due to inadequate dietary intake, gastrointestinal blood loss, or menstrual blood loss), thalassemia, or chronic disease.
A low MCV number in a patient with a positive stool guaiac test (bloody stool) is highly suggestive of GI cancer.
In iron deficiency anemia (microcytic anemia), it can be as low as 60 to 70 femtolitres. In cases of thalassemia, the MCV may be low even though the patient is not iron deficient.

All information on this page is intended for your general knowledge only and does not provide medical advice, diagnosis or treatment.