About how long does a typical human red blood cell live?

A typical human red blood cell lives for about 120 days.

Red blood cells, or erythrocytes, transport oxygen from the lungs to tissues and carry some carbon dioxide back toward the lungs. Mature human red blood cells have no nucleus and are shaped as flexible biconcave discs, allowing them to squeeze through narrow capillaries while providing a large surface area for gas exchange.

As cells age, their membranes become less flexible and their performance declines. The spleen removes many old or damaged red blood cells from circulation, while macrophages in the liver and bone marrow also help recycle them. Iron from haemoglobin is conserved and reused, and the haem component is ultimately processed into bile pigments.

The kidneys release erythropoietin when oxygen delivery is low. This hormone stimulates red-bone-marrow production of new red blood cells. Because production and removal are balanced continuously, the bloodstream maintains a large population despite each cell's limited lifespan. The 120-day figure is an average, not an exact expiry date for every cell.