What Is Blood Crossmatching?

Medically Reviewed by Carol DerSarkissian, MD on May 28, 2023
4 min read

Blood crossmatching is a series of tests that are done before a blood transfusion is performed. These tests ensure that the blood is compatible between the person giving it and the person that is receiving it.

Before a blood transfusion, your doctor will ask for blood compatibility tests, or blood crossmatching. This process is like a trial version of a transfusion using samples of blood to see how they react together. To find the best match for you, blood crossmatching helps to find blood that is close to your own for it to be a success.

If the blood isn’t a good match, your immune system could reject the donated blood, thinking that it is a foreign invader looking to harm your body. To help protect your body, your immune system could then create antibodies that fight against the new blood cells. This could then cause a dangerous reaction.

Blood crossmatching is also called blood typing or a compatibility test. Several tests are required to complete this process. The first test is blood typing, which tells you your blood type. This test also shows whether your Rh blood type is positive or negative. There are four blood groups:

  • AB
  • A
  • B
  • O

After establishing your blood type, the next step is an antibody screen. This test looks for the presence of any red blood cell antibodies that could be in your blood. The presence of these antibodies could delay the blood transfusion process if they are found.

Types of crossmatching tests. There are two types of blood crossmatching tests: major crossmatch and minor crossmatch. Major crossmatching is a mandatory test that checks to see if the blood recipient has any antibodies that might resist the donor’s blood cells. To do this test, blood cells from the donor are combined with blood serum from the recipient. Without this test, a blood bank cannot release blood donations to a patient.

Minor crossmatching is not a mandatory test. In this test, the red blood cells of the person receiving the donation are mixed with blood serum from the donor. This helps to detect antibodies that the donor may have that could work against the recipient’s antigens.

Performing the test. To do a blood compatibility test, a blood sample is taken by needle from a vein in your arm. Then, tests can be run in a lab using your blood samples, or a computer program can analyze them. Computer crossmatching can be done using results collected from antibody screens and blood group screens.

Your doctor will order this test for you if you need a blood transfusion, perhaps after a hemorrhage or an accident in which you lost a lot of blood. You could also need a transfusion after losing a lot of blood during a cesarean section (C-section), heart surgery, or renal surgery.

You may also need blood compatibility testing if you:

  • Are having an organ, tissue, or bone marrow transplant
  • Have hemophilia or another type of bleeding disorder
  • Have severe anemia or a disease that can cause it
  • Want to find out if you’re Rh positive or negative while pregnant

The results of your crossmatching test let lab staff or blood bank workers know which blood type will work the best for your transfusion.

Unlike other tests, blood typing doesn’t have any normal or abnormal results. This kind of test simply lets you know what blood type you have and if you’re Rh positive or negative. The main thing that your doctor is looking for in your results is the presence of antibodies.

If your results come back negative for any antibodies, that means that there is a good chance that you won’t have any problems accepting the blood donation that is compatible with your blood type. If there are antibodies in your blood, further lab testing has to be done to know more about them. Some antibodies can cause your blood to be incompatible with the donor’s type, but not all.

A crossmatch test can help to eliminate the possibility of a bad antigenic reaction after a blood transfusion. However, these tests can’t guarantee the possibility that your body won’t reject the donated blood.

The test itself does not have much risk involved. As with other blood samples, you might experience some pain or light bleeding when the needle is inserted into your arm. After that, your arm may feel sore and you might have some bruising at the injection site. You should also make sure to care for the area to avoid infection.

Blood transfusions themselves have several risks. You should consult with your doctor to make sure you understand all the possible risks, and so that they can answer any questions that you may have.

Show Sources


Gundersen Health System: “Crossmatch Procedure - Gel Method.”

Lab Tests Online: “Crossmatch."

OpenAnesthesia: “Blood - Crossmatch.”

UC San Diego Health: “Blood Type and Crossmatch.”

University Hospitals: “Blood Type and Crossmatch.”

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