Definition

A high red blood cell count is an increase in oxygen-carrying cells in your bloodstream. Red blood cells transport oxygen from your lungs to tissues throughout your body. A high red blood cell count can result from a condition that limits your oxygen supply or a condition that directly increases red blood cell production.

The definition of a high red blood cell count varies from one medical practice to another. A normal range in adults is generally considered to be 4.35 to 5.65 million red blood cells per microliter (mcL) of blood for men and 3.92 to 5.13 million red blood cells per mcL of blood for women. In children, the threshold for high red blood cell count varies with age and sex.