Such yummy paranoia!!!
Dude, you're not a vampire. But I agree that people can "drain" you in interactions, even regular conversations just as you can (try to) drain them. I usually respond with self-righteous anger and logic to those foolish attempts. Of course you always have the option to pack your bags and leave the table.
When you share information with colleagues and like-minded people with similar interests you would notice that you don't get drained - because there is a synergy happening, a healthy contribution of knowledge, energy and a slight euphoria of sorts.
Forcing conversation, forcing your opinion, speaking out of turn, disrespecting the person, patronizing, blaming for something/ad hominem attacks all lead to the person being drained. I'm particularly allergic to someone lying to me about me (blaming me for something I didn't do).

There are a few devil-worshiping godless freaks out there who actually drink blood. To them I can only say to stop and ask Jesus for salvation if they don't want to burn in hell for eternity. As far as you being a vampire, relax dude - you're 100% human. Which may not be much of a consolation - we romanticize ourselves to being something better, like heroes, but we're not. We're just clueless assholes looking to make sense of the world.