Real-Life Vampires: Who Are They?

But not all of his friends are vampires, and he said he also dates women outside the community.

His girlfriend, Shade, isn't sure if she's a vampire and is exploring the identity, he said. Still, she has been initiated into House Lost Haven.

As a pranic vampire, Seraphim said that he doesn't feel the need to drink blood. But, on a few occasions, he has experimented with it with people, like Shade, whom he trusts, he said..

"I had a drink of someone's blood before and got a positive experience out of it, but I don't need that to survive," he said.

Why the Desire for Blood?

Some vampires cite the so-called Renfield's syndrome, a condition used to describe an obsession to drink blood. (Renfield is the name of the fly-eating character in Bram Stoker's "Dracula.")

But this condition is not recognized in medical literature and is rejected by medical doctors, psychiatrists and psychologists.

"First of all, it absolutely, 100 percent should be discouraged by everybody. The safety issues are gargantuan," said Keith-Thomas Ayoob, an associate professor at the Albert Einstein College of Medicine in New York City.

There's an enormous risk of contracting blood-borne diseases, he said.

Underscoring the dearth of evidence for Renfield's syndrome, author Ramsland said she knows the clinical psychologist who made up the term as a joke.

But in very rare cases, she said, people suffer from clinical vampirism, which is the psychotic delusion that you need blood to survive. Convinced that they need to drink blood, she said, some people cut their own arteries or have killed loved ones.

This condition, she emphasized, is very different from forming a persona around a vampire and participating in a subculture that celebrates it.

Merticus, a 30-year-old "hybrid" vampire who is also a member of the invitation-only service group Voices of the Vampire Community, said he feeds on both energy and blood, adding that his primary feeding method is pranic and tantric-sexual, meaning that he feeds on sexual energy and arousal.

The Atlanta-based antique dealer chose not to disclose his legal name to ABCNews.com.

Although the precise reason for craving blood is unclear, vampires "cannot adequately sustain their own physical, mental or spiritual well-being without the taking of blood or vital life force energy from other sources, often human," he told ABCNews.com.

Sanguine vampires feed by drinking human or animal blood but vary in their experience of blood-hunger, he said. They typically consume an ounce or less of blood at a time, usually no more than once a week. When blood is from human sources, he said, it is consensual and facilitated through verbal or written contracts between vampires and donors.