Question: Nowadays in all hospitals, blood transfusion is given to many patients who are anemic or are undergoing operation. And it is possible that the blood of a stranger man is transfused into a lady who is na mehram or vice versa. Is it allowed in Islamic Law?
Answer: Since there is no proof for prohibition regarding this act according to the rules of Islamic Jurisprudence, there is no harm in it. Even then it is better if man is transfused with the blood of man and woman with the blood of a woman. But if this is not possible, as mentioned above, it is not haraam.