Actually, the best answer you'll get is from Marceline herself. IE- me. I don't drink human blood because A~ there is only one (not including Spitfire... She's only visiting + she's my friend) human in Ooo and that's Finn and he's a great friend. I wouldn't dream of killing him. B~ human blood is vile to me. It has a metallic flavouring. The color red simply tastes like the way the object smells. Yeah, maybe that sounds a little awkward but hey! My opinion. Plus, I don't judge what you drink, do I? No, didnt think so. So, just shows vamps won't starve without human blood. And, I'm not your stereotype of a vampire, am I? Don't see many vamps carrying axe-bass' do you? Well, that about sums it up.