In the novel Sweetblood, Pete Hautman's protagonist, a teenage diabetic, formulates the theory that vampire myths arose out of the history of untreated type 1 diabetics. Personally, I think it's a bit far fetched, but I thought it made very interesting the
Fact: Anne Rice, one of, if not the most popular vampire novelists, has a diagnosis of type 1 diabetes. I was disappointed to learn that she was diagnosed well after most of her books were written, at the age of 57, and that diabetes was not the impetus for her interest in vampires.
From interviews with her, it sounds like she doesn't have a great grasp of type 1 diabetes (but frankly, what celebrity does?), but she was diagnosed in DKA after a lengthy illness and is on a regime of multiple daily injections.
P.S. Pete Hautman was himself diagnosed with type 1 diabetes as a young adult.