Is it possible to rehydrate yourself in a life or death situation by drinking blood?

Well, not if it is your own blood, that would defeat the whole purpose. But, it might be possible. It would take a decent bit of blood to even make a cupful and it is not easy to digest. People, with stomach or intestinal problems that cause bleeding, often have upset stomachs from the blood. So, perhaps it might not make that much of a difference. Interesting question.