If your CBC test results show MCV as less than 80 femtoliters per cell, it indicates low MCV levels.
Low MCV values are usually a result of the following conditions:
Anemia of chronic disease
HbC and other hemoglobin hybrids
Iron deficiency (there are many different causes of iron deficiency or anemia)
Lead poisoning
Sideroblastic anemia
Spherocytosis
Thalassemia (there are several types.  Around 30% of African Americans are though to suffer from it.)
The most common reason for MCV levels of 70 femtoliters per cell or lower are due to lack of iron or thalassemia.