What does hematocrit measure?

Hematocrit is a laboratory test that measures the proportion of blood volume that is occupied by red blood cells, which are also known as erythrocytes. The hematocrit value is expressed as a percentage, indicating the volume of red blood cells relative to the total volume of blood.

This measurement is crucial in assessing a patient's overall health, particularly in diagnosing anemia, polycythemia, and other conditions related to blood cell production. A normal hematocrit level typically reflects adequate red blood cell production, which is vital for the oxygen-carrying capacity of the blood.

The other options focus on different components of the blood. Leukocytes, or white blood cells, are part of the immune response, and their percentage is measured in a separate test. Platelets play a role in clotting and are also measured independently. Plasma, the liquid component of blood that contains water, electrolytes, proteins, and hormones, likewise is assessed distinctly from the hematocrit measurement. Thus, the correct answer accurately reflects the specific measurement that hematocrit provides.