How can a person donate blood and never run out?

It is not biologically possible for a person to donate blood and never run out. Donating blood involves withdrawing a certain volume of blood from the donor's body. The body replaces the donated blood through a process called hematopoiesis, which takes time. While regular blood donation is possible and encouraged within specific intervals, the body needs sufficient time to replenish the lost blood volume and produce new blood cells. Therefore, a person cannot continuously donate blood without eventually depleting their blood reserves and potentially posing health risks.