The color of blood is red, if the blood circulation is not very good, or blood oxygen content is poor, and a kind of blood lipid is relatively high, then the blood at the end, found in the process of bloodletting is dark, and black may be a bit exaggerated. Usually start with a little black, but not particularly black, which proves that the circulation is not good, after putting a few drops of blood gradually become red, can not always be black, if it has been black table account symptoms are too heavy. So with bloodletting therapy can treat the disease of stagnant blood, as well as circulation is still not very good, the limbs are not warm can be improved by bloodletting to improve peripheral circulation, through the elimination of blood stasis to improve the symptoms of new.