PunkyKat wrote:
If you physicaly crave blood you could have anemia.
No. I have chronic anemia. People who are anemic can get weird craving, like for ice or certain fruits (mine is pineapple). But not for blood itself.
Blood is very poor for nutrition, high in toxic waste products from cell metabolism like urea, and could make you very ill if ingested in large qualities. So craving blood is likely a type of neurotic behavior, and could be associated with various mental illnesses.
Blood tasting--just taking in small amount of blood for pleasure--is likely just a fetish. If it's associated with scab- or skin-picking, it could be a type of Body-Focused Repetitive Behavior, like nail-biting or trichotillomania, and these behaviors are linked to the OCD spectrum.