Mean Corpuscular Volume (MCV)
Also called: MCV, Mean corpuscular volume
MCV is the average size of a red blood cell. It's the most useful single number for classifying anaemia — small, normal, or large.
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What does Mean Corpuscular Volume (MCV) measure?
MCV is calculated from the haematocrit and red cell count and reports the average size of an individual red blood cell. It transforms anaemia from "low haemoglobin" into a categorisable problem: microcytic (<80 fL) — small cells, typically iron-deficiency or thalassaemia; normocytic (80–100 fL) — chronic disease, acute blood loss, kidney disease; macrocytic (>100 fL) — vitamin B12 / folate deficiency, alcohol, hypothyroidism, certain medications. The MCV breakdown drives the next diagnostic step before any second-tier test.
What does a high Mean Corpuscular Volume (MCV) level mean?
- Vitamin B12 deficiency — macrocytic anaemia; check B12 and methylmalonic acid.
- Folate deficiency — same picture; check folate.
- Alcohol — common, even without overt liver disease.
- Hypothyroidism — TSH should be checked when MCV is elevated without obvious cause.
- Myelodysplastic syndromes, drug-induced — hydroxyurea, methotrexate, zidovudine.
- Reticulocytosis — young red cells are larger; recent blood loss or haemolysis.
What does a low Mean Corpuscular Volume (MCV) level mean?
- Iron-deficiency anaemia — the textbook microcytic anaemia.
- Thalassaemia trait — often discovered incidentally; microcytic out of proportion to mild anaemia.
- Anaemia of chronic disease — usually normocytic but can become microcytic.
- Lead poisoning — increasingly rare but worth knowing.
When to discuss with a doctor
MCV outside the normal range in the context of anaemia drives the workup: ferritin if microcytic, B12 and folate if macrocytic. A persistent MCV abnormality without anaemia should still be investigated — it can be the earliest sign of impending deficiency or a haematologic process. Mediora.AI uses MCV to route the anaemia interpretation in your report.
Related markers
Commonly confused with
- Mean Corpuscular Hemoglobin (MCH) Both describe the average red cell, which is why they are read together and mixed up. MCV is its size; MCH is how much haemoglobin is inside it. Small cells with little haemoglobin point at iron; large cells point at B12 or folate.