See here: http://mi.yodeya.com/questions/1188/kashering-a-knife
"The consumption of human presents a number of halachic problems/prohibitions but they are not related to kashrus strictly speaking.
Human blood is prohibited because of Maris Ayin, it is not even strictly speaking a "Rabbinic prohibition". As such there is, I believe, no concept of tam k'ikkar (the taste is like the forbidden substance). As such while it is prohibited to eat bread which has blood from one's gums on it, such blood would not impart a forbidden taste to utensils. (Shulchan Aruch, Yoreh Deah 66:10)"
As mentioned, blood from one's gums isn't a problem unless it leaves one's mouth in which case it looks like one is eating blood and is prohibited due to ma'aris ayin.
Since tam/taste is not the issue it is possible that it is not a problem to suck blood from a wound when once spits it out immediately. Obviously if there is a real sakana it is permitted. I'll try to find sources that deal with it more directly.