Blood transfusion in Islam is allowed under extreme and dire circumstances; such as when a person is involved in a serious accident or attack, resulting in severe loss of blood. In such a case, normally a person will not survive without the introduction of blood into the body. People who are critically wounded often die due to loss of blood. So when life is threatened then blood transfusion becomes necessary.
The basis of the law is verse 173 of Surah Baqarah wherein Allah Ta'aala states:
HE HAS ONLY FORBIDDEN YOU DEAD MEAT AND BLOOD AND THE FLESH OF SWINE AND THAT ON WHICH ANY OTHER NAME HATH BEEN INVOKED BESIDES THAT OF ALLAH; BUT IF ONE IS FORCED BY NECESSITY WITHOUT WILFUL DISOBEDIENCE, NOR TRANSGRESSING DUE LIMITS, THEN THERE IS NO SIN UPON HIM. VERILY ALLAH IS OFT-FORGIVING, MOST MERCIFUL.
Blood is an impure substance, so by right its use should not be permissible. However, drawing an analogy from breast milk, which is Haraam to consume for a human older than two years of age, but permissible to use as a medicine, the Ulama declare that due to an urgent and dire need, the use of blood as medical treatment will be lawful. This should only be as a last resort and when there is overwhelming evidence that the patient will die should he not be administered blood transfusion.
BLOOD OF A NON MUSLIM
Based on the above, the transfusion of non-Muslim blood will also be permissible. However, the Fuqahaa (Jurists of Islam) have stated that although permissible, parents should not allow non-Muslims to breastfeed their infants because the effect of their Kufr infiltrates the system of the baby via the milk. On the other hand, it is stated in the Books of Jurisprudence that the milk of a pious woman has a wonderful effect upon the suckling baby. Blood transfusion could be judged in the same manner.
Mufti Siraj Desai