Although the Bible does not specifically mention this medical practice, we do not believe God will condemn one for having a transfusion. Some religious groups have misinterpreted God's command against eating blood (Leviticus 3:17), mistakenly extending it to receiving blood by transfusions. Ingesting blood and receiving it into the circulatory system are not the same thing. God specifically commands against the eating of blood, a prohibition reiterated in the New Testament as tied to idolatrous worship (Acts 15:19-20, 29).
While having a transfusion is not a sin, a proficient doctor would advise that medical risks are involved, as in any transmission of bodily fluids. Thus, one ought to weigh these risks and the anticipated benefits carefully.