Blood typing is also done to tell whether or not you have a substance called Rh factor on the surface of your red blood cells If you have this substance, you are considered Rh+ (positive). Those without it are considered Rh- (negative). Rh typing uses a method similar to ABO typing.

No special preparation is necessary for this test.

Some people have discomfort when the needle is inserted. Others may only feel a tiny prick or stinging sensation. Afterward, there may be some throbbing or a bruise may develop.

This test is done to determine a person's blood type. Health care providers need to know your blood type when you get a blood transfusion or transplant, because not all blood types are compatible with each other. For example:

• If you have type A blood, you can only receive types A and O blood.
• If you have type B blood, you can you can only receive types B and O blood.
• If you have type AB blood, you can receive types A, B, AB, and O blood.
• If you have type O blood, you can you can only receive type O blood.

Type O blood can be given to anyone with any blood type. That is why people with type O blood are called universal blood donors.

Blood typing is especially important during pregnancy. If the mother is found to be Rh-, the father should also be tested. If the father has Rh+ blood, the mother needs to receive a treatment to help prevent the development of substances that may harm the unborn baby. See: Rh incompatibility

If you are Rh+, you can receive Rh+ or Rh- blood. If you are Rh-, you can only receive Rh- blood.

Images

Erythroblastosis fetalis, photomicrograph

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Review Date: 02/05/2010
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)