The two aren't related directly in the way "more food - more blood, less food - less blood" The things you eat and drink provide you with the energy to keep up all functions you need to survive - about 20% of the energy for example is just needed by your brain to continue working. The replacement of blood cells works the same way. Your body needs to replace the blood cells after a while anyway, and if there is a blood loss additional blood cells need to be produced. However, this works even if you are starving as the circulatory system is one of the core functions to stay alive.

How long it takes to replace the blood was already answered by the other comment