It hurt and he felt weak, but he wasn't dead. It wasn't something he was going to repeat anytime soon though. His arm was already healing and he could feel new blood coming back to his veins. Stiles had taken a lot, obviously.

"I'm fine. I've been hurt worse," Derek snapped, not letting the scrawny boy know how dangerous he was.

"How do you feel?" he asked hoping the answer would be satisfied. If not, if the only satisfaction was drinking to the point of death then Derek might just have to put him down for good.