Blood Typing

Written by Brian Krans | Published on July 18, 2012
Medically Reviewed by Brenda B. Spriggs, MD, MPH, FACP

Overview

Blood typing is a test that determines a person’s blood type. The test is essential if you need a blood transfusion or are planning to donate blood. Not all blood types are compatible, so it is important to know your blood group to ensure that if you are given a transfusion your body doesn’t make antibodies to attack the donor blood.

The Blood Types

The ABO blood typing system groups your blood into one of four categories:

  • O: type O individuals can donate blood to anyone, but can receive blood only from other type O individuals.
  • A: type A individuals can donate to other type A individuals and type B individuals. Type A individuals can receive blood only from other type A individuals and type O individuals.
  • B: type B individuals can donate blood to other B individuals and AB individuals. Type B individuals can receive blood only from type B individuals and type O individuals.
  • AB: type AB individuals can give blood only to other AB individuals, but can receive blood of any type.

Then, there is the Rh factor blood grouping system:

  • Rh+: People with Rh-positive blood have Rh antigens on the surface of their red blood cells. People with Rh+ blood can receive Rh+ or Rh- blood.
  • Rh-: People with Rh-negative blood do not have Rh antigens. People with Rh- blood can receive only blood that is also Rh-.

Together, the ABO and Rh grouping systems yield your complete blood type. There are eight possible types: O+, O-, A+, A-, B+, B-, AB+, and AB-.

Austrian Karl Landsteiner discovered blood types in 1901. Before that, blood transfusions were risky and potentially lethal. Landsteiner made the process much safer, and he was awarded the Nobel Prize for his work.

Why Blood Typing Is Done

Blood typing is done prior to a blood transfusion or when classifying a person’s blood for donation. Blood typing is a fast and easy way to ensure that you receive the right kind of blood during surgery or after an injury. If you are given incompatible blood, it can lead to blood clumping, or agglutination, which can be fatal.

Blood typing is especially important for pregnant women. If the mother is Rh- and the father is Rh+, the mother and child will have different blood types. In these cases, the mother needs to receive a drug called RhoGAM. This drug will keep her body from attacking the baby’s blood cells if their blood becomes mixed, which often happens during pregnancy.

The Risks of Blood Typing

You will need to have your blood drawn in order to have it typed. Having your blood drawn carries a very minimal risks, including:

  • bleeding under the skin (hematoma)
  • fainting or feeling light-headedinfection at the puncture site
  • excessive bleeding

How to Prepare for Blood Typing

No special preparation is needed for blood typing. If you think you might feel faint during the test, you may want to have someone else drive you home afterward.

How Blood Typing Is Performed 

The blood draw can be performed at a hospital or a clinical laboratory. Your skin will be cleaned before the test with an antiseptic to help prevent infection. A nurse or technician will wrap a band around your arm to make your veins more visible. He or she will use a needle to draw several samples of blood from your arm or hand. After the draw, gauze and a bandage will be placed over the puncture site.

In order to determine your blood type, a lab technician will mix your blood sample with antibodies that attack types A and B blood to see how it reacts. If your blood cells clump together when mixed with antibodies against type A blood, for example, you have type B blood. Your blood sample will then be mixed with an anti-Rh serum. If your blood cells clump together in response to the anti-Rh serum, it means that you have Rh+ blood.

After Blood Typing

Your blood type can be determined in a matter of minutes. Once you know your blood type, you can donate blood and receive transfusions from donors in the compatible blood groups.

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