CPT (Certified Phlebotomy Technician) Practice Exam

The lifespan of a red blood cell (RBC) is approximately 90 to 120 days. During this time, the RBCs circulate within the bloodstream, transporting oxygen from the lungs to the tissues and returning carbon dioxide back to the lungs for exhalation. After this period, the cells are generally phagocytized by macrophages in the spleen and liver, ensuring the body's production and replacement of fresh RBCs remains efficient.

The other ranges provided in the options do not accurately reflect the typical lifespan of RBCs. For example, a lifespan of 30 to 60 days or 60 to 90 days falls short of the standard, while 120 to 150 days extends beyond the accepted duration. The correct answer accurately represents the well-established duration of RBCs in human circulation.