What is the average lifespan of a red blood cell?

The average lifespan of a human red blood cell is about 120 days.

Red blood cells, also called erythrocytes, circulate continuously while transporting oxygen from the lungs to tissues and carrying some carbon dioxide back toward the lungs. Mature human red blood cells lack a nucleus and most internal organelles, leaving more room for hemoglobin. That design helps them bend through narrow capillaries but limits their ability to repair themselves.

New red blood cells are produced in the bone marrow through a process called erythropoiesis. The transition from developing cell to mature red blood cell takes about seven days. Adults produce roughly 2.4 million new erythrocytes every second to replace cells that are aging or being removed.

A lifespan of 120 days is a useful rounded figure; many references give a normal range of about 100 to 120 days. Aging cells become less flexible and are recognized by macrophages, especially in the spleen, liver, and lymph nodes. Their iron and other components are recycled. Red-cell survival can be shorter in chronic disease, blood loss, or certain inherited disorders, so 120 days describes a healthy typical average rather than an unchanging rule for every person.