MCV

Understanding the marker

MCV measures the average size of red blood cells. It adds information to haemoglobin and the other blood-count measurements.

Smaller or larger red cells can help guide the investigation of a blood-count change. Iron, B12 and folate tests may add context. A cell size within the interval does not exclude a deficiency, particularly when more than one factor affects the cells.

What does high MCV mean?

High MCV means the red cells are larger on average. B12, folate, medicines and other factors can affect cell size. The complete blood count and relevant tests help distinguish the possibilities.

What does low MCV mean?

Low MCV means the red cells are smaller on average. Iron availability is one possible influence, but haemoglobin, iron tests and previous results are needed to assess the cause.