The lifespan of a red blood cell is approximately how long?

• A. 2 weeks
• B. 4 months
• C. 1 year
• D. 6 months

Answer: (B)

Red blood cells circulate for about 120 days, which is roughly four months. They lack nuclei and have limited repair capability, so as they repeatedly squeeze through small capillaries they accumulate membrane damage over time. This leads to their removal by the spleen and recycling of their components. To maintain oxygen transport, the bone marrow continuously makes new red blood cells through erythropoiesis and releases them as reticulocytes that mature within a day or two. So four months best matches the known lifespan of circulating red blood cells. Durations like two weeks, six months, or a year don’t align with how long mature red blood cells typically last in the bloodstream.