Does your body use the same blood until you bleed out or does it naturally get rid of it while making more. if so how does it get rid of it?

120 days: Your body replaces red blood cells about every 120 days - of course, not all at once - but each cell is replaced. As it normally passes through lymph tissues (nodes, spleen), the "old" red blood cells are pulled out and a built-in self-destruct sequence called apoptosis is activated. The cell components are recycled for new cells. The heme is excreted in your stool which is what makes it brown.