A blood substitute (also called artificial blood or blood surrogates) is a substance used to mimic and fulfill some functions of biological blood. It aims to provide an alternative to blood transfusion, which is transferring blood or blood-based products from one person into another. Thus far, there are no well-accepted oxygen-carrying blood substitutes, which is the typical objective of a red blood cell transfusion; however, there are widely available non-blood volume expanders
for cases where only volume restoration is required. These are helping
doctors and surgeons avoid the risks of disease transmission and immune
suppression, address the chronic blood donor shortage, and address the
concerns of Jehovah's Witnesses and others who have religious objections to receiving transfused blood.