I agree that Paul's words refer to murder. Also l believe that there was a rather vile practice at the time of people drinking the blood of dying gladiators in the belief that they would gain the strength of that gladiator . So that would be forbidden.
Jews have no problem taking transfusions because
a) it's blood from a human being who is still alive , not a creature which has died to provide food or as a sacrifice.
b) the preservation of human life is a sacred duty.
Jan