Normal Mean Corpuscular Volume (MCV)
The normal range for Mean Corpuscular Volume (MCV) in adults is 80-100 femtoliters (fL). 1
Understanding MCV Values
MCV is a measurement of the average size of red blood cells and serves as an important parameter in the complete blood count (CBC). It helps categorize anemias and other hematologic conditions:
Microcytic (MCV < 80 fL): Most commonly caused by iron deficiency; other causes include thalassemia, anemia of chronic disease, and sideroblastic anemia 1
Normocytic (MCV 80-100 fL): May be caused by hemorrhage, hemolysis, bone marrow failure, anemia of chronic inflammation, or renal insufficiency 1
Macrocytic (MCV > 100 fL): Most commonly megaloblastic, indicating vitamin B12 or folate deficiency; non-megaloblastic causes include alcoholism, certain medications (hydroxyurea, diphenytoin), and myelodysplastic syndrome 1, 2
Age-Specific Considerations
Adults: Normal MCV range is 80-100 fL 1
Children: Normal MCV values are lower than adult values and increase gradually with age 3:
- 10-17 months: Lower limit of normal is 70 fL
- 1.5-4 years: Lower limit of normal is 74 fL
- 4-7 years: Lower limit of normal is 76 fL
Clinical Significance of MCV Values
Elevated MCV (>100 fL)
Common causes: Vitamin B12 deficiency, folate deficiency, alcoholism, liver disease, medications (hydroxyurea, azathioprine, 6-mercaptopurine), and myelodysplastic syndrome 2, 4
Clinical significance: MCV values >100 fL in patients with liver disease almost invariably indicate alcohol-related disease 5
Diagnostic approach: Should include peripheral blood smear examination, reticulocyte count, and measurement of vitamin B12 and folate levels 2, 6
Low MCV (<80 fL)
Common causes: Iron deficiency, thalassemia, anemia of chronic disease 1
Clinical significance: In thalassemia carriers, parents can be screened by evaluation of MCV, which will be <80 fL in thalassemia carriers 1
Important Considerations in MCV Interpretation
Inflammation: MCV values can be influenced by inflammation, which should be considered when interpreting results 1
Reticulocyte count: A key follow-up test for normocytic anemia to distinguish between decreased production versus increased destruction or loss of red blood cells 1
Peripheral blood smear: Critical for confirming the size, shape, and color of RBCs and should be performed when evaluating abnormal MCV values 1, 6
Clinical context: MCV should always be interpreted in the context of other laboratory findings and the patient's clinical presentation 7, 6
Common Pitfalls in MCV Interpretation
Failure to recognize macrocytosis: Studies show that clinicians often fail to evaluate macrocytosis, particularly when MCV values are only modestly elevated (98.5-100.6 fL) 7
Missing underlying conditions: Clinically significant and treatable diseases (like vitamin B12 deficiency, hypothyroidism) are often associated with macrocytosis and may be missed without proper evaluation 7
Overlooking medication effects: Many medications can cause macrocytosis independent of nutritional deficiencies 2
Ignoring mixed disorders: Concurrent conditions (e.g., iron deficiency with vitamin B12 deficiency) may result in a normal MCV despite significant pathology 6