Blood is not a medicine, but it is a fundamental part of getting treated in a hospital. Some people will need blood transfusions in order to survive a hospital stay. That does not necessarily make it a "Medicine" per se. Sure, it has it's use, but it doesn't have the same effect as "medicine."
Several religions do not allow for donation of or acceptance of blood. They have this right and as such they have done research on how to receive treatment without the use of blood and some would argue that they are healthier and recover faster because of it. Of course everyone looks for evidence that supports their argument.
Blood in medical use is made possible through donations from individuals. If you make it an essential medicine, in order to always have enough on demand, you would need to require people to give blood, which is not ethical to do. Giving blood is helping to save a life, but it is not a "cure-all" and blood donations do not always save a person.
I don't feel that it is a medicine, it is more of a life source that is not man made. If blood is a medicine so is water and air. I feel that blood is above medicine, it is needed for life not to treat.