How much blood can I give?

Today was a big day in the life of this lab rat.  My CA125 was down, cancer was stable, so I was allowed to go on to the next two rounds of treatment.  I had blood drawn yesterday, and five or six blood draws today as I started cycle 3.  Blood draws tomorrow and thursday in the morning.  How much blood do I have and how quickly can it be replaced when I am already anemic?  I guess they, the vampires of the study world,  know our bodies can do it.  In the meantime I am relieved but exhausted, hoping for a long hot summer where I feel well enough to enjoy it.