Which formed element is most abundant in healthy human blood?

• A. Red blood cells
• B. White blood cells
• C. Platelets
• D. Plasma

Answer: (A)

Understanding blood components: formed elements are the cellular parts—red blood cells, white blood cells, and platelets—while plasma is the liquid portion. Among the formed elements, red blood cells are by far the most numerous in healthy blood, reflecting their critical role in oxygen transport with hemoglobin. Typical counts show millions of red blood cells per microliter, whereas white blood cells are only thousands, and platelets are hundreds of thousands per microliter. Plasma, though it makes up a large volume of blood, is not a formed element. So the most abundant formed element is red blood cells.