At one time, type O negative blood was considered the universal blood donor type. This implied that anyone — regardless of blood type — could receive type O negative blood without risking a transfusion reaction. But it's now known that even type O negative blood may have antibodies that cause serious reactions during a transfusion. And blood transfusions in general carry some risk of complications.
Blood may be classified as one of these four types:
- Type A
- Type B
- Type AB
- Type O
Blood is also classified by rhesus (Rh) factor, which refers to a specific red blood cell antigen in the blood. If your blood has the antigen, you're Rh positive. If your blood lacks the antigen, you're Rh negative.
Ideally, blood transfusions are done with donated blood that's an exact match for type and Rh factor. Even then, small samples of the recipient's and donor's blood are mixed to check compatibility in a process known as crossmatching.
In an emergency, type O negative red blood cells may be given to anyone — especially if the situation is life-threatening or the matching blood type is in short supply.
Jan. 14, 2016
See more Expert Answers
- Kleinman S. A primer of red blood cell antigens and antibodies. http://www.uptodate.com/home. Accessed Nov. 20, 2015.
- Blood FAQ. American Association of Blood Banks. http://www.aabb.org/tm/Pages/bloodfaq.aspx. Accessed Nov. 20, 2015.
- Goldfinger D, et al. The incompatible crossmatch. http://www.uptodate.com/home. Accessed Nov. 20, 2015.
- Tintinalli JE, et al. Transfusion therapy. In: Tintinalli's Emergency Medicine: A Comprehensive Study Guide. 7th ed. New York, N.Y.: The McGraw-Hill Companies; 2011. http://www.accessmedicine.com. Accessed Nov. 20, 2015.