If you’ve lost blood, either by a severe cut or donating to a blood bank, your body can generate new blood to replace it. How does your body know when it needs more, and how does it know when to stop so you don’t end up with an excess amount?

Question

If you’ve lost blood, either by a severe cut or donating to a blood bank, your body can generate new blood to replace it. How does your body know when it needs more, and how does it know when to stop so you don’t end up with an excess amount?

In: Biology

Answer 1

There is a hormone produced by the kidney called erythropoietin. That hormone makes the blood marrow produce more red blood cells.
When there isn’t enough oxygen reaching the kidney (because of the lost blood), it produces this hormone so more blood is made.

TL;DR: the kidney tells the blood marrow to make more blood