The cells eventually die and are absorbed into the body as the bone morrow found in the pelvic bone makes the new ones. Recycle!
Poop is brown for a reason.
I came in to say this.
Have you ever taken a general biology, psychology, or neurobiology course? Your brain is always working hard and will always need the energy and oxygen it derives from erythrocytes (red blood cells). If a specific area in the brain does not "need" the excess, it will redirect the blood flow to an area of the brain that does need the supply of oxygen. Red blood cells break down in the liver anytime between 5-200 days of circulation in the body.
Wait, I just realized I answered your question thinking that you'd wrote "What does the BRAIN do with the extra red blood cells it doesn't need?" Oh well...
Ever wonder why poop is brown??? Now you know.
donate your blood every 4 months..It gets rid of those old cells, jumpstarts you marrow to make new, healthier one
and, you get to help so so many people.
The body has a kind of self limiting system which allows excess minerals such as iron to be excreted, rather than retained for the making of red blood cells. If you have enough then only the number needed to replace dying ones is created. In fact there is a genetic disorder called Hemachromatosis where the excess iron is not excreted, but stored in the organs, where it can cause organ faulure from the age of about 50. So even if you have too much iron, it is still not turned into extra red blood cells. Just stored.
I'm pretty sure your liver filters them out and your body reabsorbs them to make other cells and such.
I believe they get destroyed but I'm not 100% sure on that.
Red blood cells last about 4 months.