Blood type test

Blood type tests are used to check what blood type you have. Your blood is "typed" according to whether certain markers, called antigens, are present on the surface of red blood cells.

The two most common blood type tests are the ABO and Rh tests. The ABO test shows which of four blood types you have: A, B, AB, or O. These letters stand for which kind of antigen you have on your red blood cells. If your red blood cells do not have either the A or B antigen, you have type O blood.

An Rh test checks for the Rh antigen (or Rh factor). It is done in early pregnancy to check a person's blood type. Problems can occur when someone who has Rh-negative blood becomes pregnant with a baby (fetus) that has Rh-positive blood. If this happens, treatment is available to help avoid these problems.

A blood type test is done:

• To help check whether jaundice in a newborn might be serious. If a baby's blood type is different from the blood type of the person who gave birth, the risk is higher.
• Before a child gets a blood transfusion.
• Before a child has surgery.

A health professional uses a needle to take a blood sample, usually from the arm.

In general, there's nothing you have to do before this test, unless your doctor tells you to.

Blood type tests are done before a person gets a blood transfusion and to check the blood type of someone who is pregnant. The following table shows the compatibility of blood types between blood donors and recipients.

Read the table as follows: A person who has A-negative blood can receive A-negative or O-negative blood.

Minorantigens(other than A, B, and Rh) on the red blood cells are also checked for a match before a blood transfusion.