How Do Vampires Feed?

Answer 1

Umm By biting you ? What did you think they did ?

Biting is actually the last resort of a vampire. Human teeth are not well suited to cause bleeding. (unless you have shape-shifting abilities like Count Dracula). Most employ small knives or large needles.

Answer 2

This is a difficult question to answer as vampires have a constant hunger and often feed far more than what they need to. Some vampires become gluttons and grow corpulent (read 'The Shunned House' by Edgar Allen Poe) but such monsters are usually destroyed quickly as they draw attention to themselves and are awkward to say the least. Count Dracula constantly acted as if he was restraining himself.

And yet, vampires have remained buried for hundreds of years without too much obvious detriment to their physique and have arisen whole and capable of predation.

Sorry not to be of much help. I guess the best advise I can give is to closely monitor their appearance. Starvation with degrade a vampires physique. But then don't restrain them to much or they will revolt and desert you.