I have never heard of blood magic, and I don't understand what you mean. I'm guessing you mean incorporating blood with magical workings, and doing so is binding yourself (or whoever's blood it is) to the working.
I have also heard about using women's menstrual blood in hoodoo, but I'm not too sure.
Though just saying, if you're using your own blood, remember: safety first.
Feel free to correct me if you like, I'm not 100% sure.