ATI Pathophysiology Practice Exam 2025 – All-in-One Guide to Master Your Exam Success!

The measurement of the percentage of red blood cells in whole blood is referred to as hematocrit. Hematocrit is determined by centrifuging a sample of blood, causing the components to separate by density. The portion of the blood that consists of red blood cells is measured and expressed as a percentage of the total blood volume. This measurement is vital for assessing conditions such as anemia or polycythemia, where the number of red blood cells is either significantly lower or higher than normal, respectively.

In contrast, hemoglobin refers to the protein in red blood cells that carries oxygen, and while it provides important information about the blood's oxygen-carrying capacity, it is not a measure of the volume percentage of red blood cells. The leukocyte count measures the number of white blood cells in the blood, which is an indicator of immune function rather than red blood cell volume. Erythropoietin level is a hormone produced by the kidneys that stimulates red blood cell production; measuring its level can help evaluate bone marrow activity but does not reflect the existing percentage of red blood cells in the bloodstream.