According to some Muftis, it is permissible to donate blood.

Answer

We differ with the opinion regarding 'donation' of blood. Under no circumstances is it permissible to donate blood, faeces or urine. In an emergency when there is no medicine/remedy available, not even a haraam medicine, then we are to rely on Dua and resign ourselves to Allah's decree.

Tadaawi bil haraam (treating with haraam substances) applies to a haraam substance on hand at the time of emergency. It does not legalize the commission of a haraam act such as 'donating' blood, faeces, urine and pork to be saved in 'banks'.

In a state of dire emergency what will the doctors do if the only blood available is contaminated with HIV or other diseases? What will they do if no blood at all is available? Allah's decree will take its course. If suitable blood is not forthcoming, and if there is no other remedy, the doctors advise the family to have the life-sustaining machine switched off and to take their patient home since they are unable to do anything for him. Thus, when no remedy is available, and the patient dies, it should not be the doctor's concern. Maut arrives at its stipulated time as the Qur'aan declares: "No person will die except at the appointed time." Doctors are also required to operate within the confines of the Shariah. Such operation is more important than the baseless idea of a life being saved with haraam medicine. The haraam remedy will not prolong life by one second. In all activities of life, the Muslim should be governed by the Shariah and by his Aqeedah. His belief should be that one dies only at one's appointed time.