What percentage do red blood cells account for in blood makeup?

Red blood cells account for approximately 45% of the total blood volume in a healthy adult. This percentage is often referred to as the hematocrit level, which measures the proportion of blood that is occupied by red blood cells. The primary function of these cells is to transport oxygen from the lungs to the tissues and carry carbon dioxide from the tissues back to the lungs for exhalation.

Understanding hematocrit is essential in clinical settings, as deviations from this normal range can indicate various health issues. For instance, a lower percentage may suggest anemia, while a higher percentage might indicate dehydration or conditions that lead to an increased production of red blood cells.

Other options such as 30%, 55%, and 70% do not accurately represent the typical composition of blood in healthy individuals. Blood is composed of plasma, red blood cells, white blood cells, and platelets, with plasma making up about 55% of blood volume, while red blood cells occupy about 45%. Therefore, the choice indicating 45% aligns with the established understanding of blood composition.