Last week we discussed how January is blood donation month, and went over the process of blood donation. This week we’ll take a look at blood and how to classify it.

In the past it was believed our blood was blue inside our body, but that when it came out either through venipuncture or a cut, it instantly turned red due to the oxygen in the air. This is a myth. Blood is already in contact with oxygen inside our bodies once it passes through the lungs. The only difference in color is perhaps that the “de-oxygenated” blood in our veins is dark red or maroon colored, while the oxygen rich blood in our arteries is bright red.

Blood is classified by which antigens its red blood cells possess. The two antigens are A and B. Type A blood contains the A antigen, type B blood contains the B antigen, type AB contains both the A and B antigen, and type O blood contains neither the A or B antigen.

In addition to the A and B antigens, there is also something known as the “Rhesus Factor,” better known as the Rh factor. Generally a person’s blood either contains the Rh factor, or it doesn’t. This is where the + or – symbol comes from in your blood type. Although blood type percentages vary by ethnicity, type O is generally regarded as the most popular blood type, followed by type A, then type B, and finally type AB being the least common.

Blood compatibility can seem quite complicated, but really there are just a few guidelines to go by. The first thing to remember is that Rh negative patients can only receive Rh negative blood, but Rh positive patients can receive either Rh positive or negative blood.

Another easy tool to remember is that type O blood is the universal donor, while type AB blood is the universal recipient. Each blood type can receive its own blood type, or type O, as long as the Rh factor is compatible. Type O blood, while it is the universal donor, can only receive type O blood.

Here is a simple list of what blood types can be donated to whom, assuming the Rh factor is compatible. Type O patients can only receive type O blood. Type A patients can receive type A blood or type O blood. Type B patients can receive type B blood or type O blood. Type AB patients can receive type A, type B, type AB, or type O blood.

Check back next week when we will be discussing how a baby’s blood type is determined by the parent’s two blood types.

Justin Glaze is an LPN and contributing columnist for the Walker County Messenger. He can be reached at 678-988-1011 or jglazelpn@yahoo.com.