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 only 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 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.