The fluid to cellular ratio of blood is what to what, respectively?

• A. 50% to 50%
• B. 55% to 45%
• C. 60% to 40%
• D. 45% to 55%

Answer: (B)

Blood is made up of a liquid part, plasma, and the cellular components (red cells, white cells, and platelets). In a healthy adult, the plasma volume is slightly more than half of the blood, about 55%, while the formed elements occupy roughly 45%. This reflects the typical hematocrit values seen for red cells, with plasma providing the remaining volume. Therefore, the fluid to cellular ratio is about 55% to 45%. Some variation can occur with hydration, sex, or physiology, but 55% to 45% is the standard teaching.