Mean Corpuscular Volume
MCV· also: Mean Cell Volume
Clinical Overview
MCV is the average volume of individual red blood cells, measured in femtoliters (fL). It is the most important red cell index for classifying anemia as microcytic (small cells, low MCV), normocytic (normal cells), or macrocytic (large cells, high MCV). Each category has a distinct set of causes that guides further investigation.
Why This Test Matters
MCV is the primary tool for narrowing the differential diagnosis of anemia. A low MCV points to iron deficiency or thalassemia; a high MCV points to B12/folate deficiency or alcohol excess; a normal MCV with anemia suggests chronic disease, renal anemia, or early mixed deficiency. MCV also screens for alcohol misuse — it is often elevated in heavy drinkers even without anemia.
Reference RangesWHO/IFCC standards
| Age Group | Reference Range | Unit | Notes |
|---|---|---|---|
| Adults (18–64) | 80 – 100 | fL | — |
What Causes Abnormal Results?
High MCV Causes
- Vitamin B12 deficiency
- Folate (folic acid) deficiency
- Alcohol excess (direct toxic effect on red cells)
- Hypothyroidism
- Liver disease
- Certain medications (methotrexate, hydroxyurea, zidovudine)
- Myelodysplastic syndrome
- Reticulocytosis (young cells are larger)
Low MCV Causes
- Iron deficiency anemia (most common cause of low MCV)
- Thalassemia (alpha or beta)
- Anemia of chronic disease (occasionally)
- Lead poisoning
- Sideroblastic anemia
Signs & Symptoms to Watch For
How to Prepare for This Test
No special preparation required. MCV is calculated automatically from the CBC and is not affected by fasting status.
Factors That Can Affect Results
- Hyperglycemia (high blood sugar causes RBC swelling in EDTA tube, raising measured MCV)
- Cold agglutinins (RBC clumping raises apparent MCV)
- Reticulocytosis (young cells are larger, raising MCV)
- Mixed deficiency (iron + B12 together can give a falsely normal MCV)
Related Topics
Frequently Asked Questions
What does a high MCV mean?
A high MCV (macrocytosis, above 100 fL) means red blood cells are larger than normal. The most common causes are vitamin B12 deficiency, folate deficiency, and alcohol use. Hypothyroidism, liver disease, and some medications (methotrexate, hydroxyurea) also cause macrocytosis. When combined with anemia, this is called macrocytic anemia and warrants B12 and folate testing.
What is the difference between MCV and MCH?
MCV measures the size (volume) of individual red blood cells. MCH (mean corpuscular hemoglobin) measures the average amount of hemoglobin per cell. They often change together — in iron deficiency, both MCV and MCH are low (microcytic hypochromic anemia). MCHC (mean corpuscular hemoglobin concentration) measures hemoglobin concentration per cell.
Can normal MCV rule out anemia?
No. Normocytic anemia (normal MCV with low hemoglobin) is common and includes anemia of chronic disease, early iron deficiency, hemolytic anemia, kidney disease, and bone marrow failure. A normal MCV simply tells you the cell size is normal, not that anemia is absent.