"There's a very distinct difference between blood types in people. The synthetics try to duplicate it, but they don't get it quite right." He was pretty sure that wasn't what Sam wanted to know. He picked at the label on the bottle. "I dunno how reliable a source I am, though... I mean, besides you, I've only drank from maybe three people, but some are very different. And things that affect the blood, like drinking alcohol or taking drugs, can carry over. I got a pretty good buzz off a girl from a bar a while back."