How much blood can a vampire drain from one human being?

Question

How much blood can a vampire drain from one human being?

Answer 1

In most people there is from 5 to 5.6 liters of blood.  Any self-respecting vampire would drain it all.

Answer 2

Assuming a vampire could drain all the blood from the human body, it could drain 5 pints of blood from a human being.

Answer 3

all of it of course

Answer 4

I am going to go by calories of a regular human male for reference. An average human male needs about 2500 calories a day right, well since a vampire is twice as strong lets assume it needs double that. So i would think that blood is about as effective as sugar it should be about the same. so according to my calculations lol a regular person needs .82 pounds sugar so .82 time 2  is 1.64 pounds of blood a day. so 1.64 assuming the vampire does the bare minimum.