Every person has a specific blood type. To determine your type, the makeup of your red blood cells is analyzed to search for specific proteins, called antigens, in your bloodstream. Not all blood types are compatible, however. This information is critical, especially involving certain medical conditions. Let’s look at the different blood types and the concerns that they present.

How Is Blood Type Determined?

In order to find out what kind of blood you have, you need to have a blood type test. Testing has become so easy these days that you can order the test online and go to a nearby walk-in lab to have the test taken. Often, the test is performed the same day it is ordered.

There are four main categories of blood type, including:

  • Antigen A – If your blood has this antigen, your blood type is A.
  • Antigen B – The B antigen in your blood signifies that your blood is type B.
  • Both antigen A & B – Both antigens in your blood mean your blood type is AB.
  • Neither antigen A nor B – If neither the A or B antigen is present, your blood type is O. This is the most common blood type.

In addition to the four categories of blood, a Rhesus-negative (Rh) antigen factor must also be considered. If your blood contains this Rh antigen, it is Rh-positive. If no Rh antigen is found in your blood, you are Rh-negative. The Rh negative blood type can be administered to a person who has either the negative or positive Rh type of blood. 

Why is Blood Type Important?

All blood types aren’t compatible with each other. This is significant in certain medical circumstances. If a person requires a blood transfusion or they require additional blood during surgery, the health care professional must make sure the patient is given blood that is compatible with their specific type of blood. Otherwise, serious health conditions may result. To reduce the risk of organ rejection in transplant patients, organs must be given by donors with a blood type that is compatible to the patient’s.

If a new mother-to-be has a different blood type than her child, the doctor must keep an eye on the situation and provide proper treatment when necessary to ensure the baby stays healthy. For example, it is possible during the pregnancy for the red blood cells from the mother to enter the placenta or the fetus. The mother’s blood cells then begin to develop certain antibodies that cause jaundice when the baby is born. Knowing this information ahead of time will prepare the baby’s doctor for proper treatments at birth, if needed.

Pregnant women must also be aware of incompatibility of Rh in their blood, which might result in a serious disorder called Erythroblastosis fetalis. This happens when an Rh-negative mother is pregnant with a Rh-positive baby. When this occurs, the doctor must monitor the health of the growing fetus very closely. 

Certain health concerns can be triggered by blood type as well. Knowing this information is helpful to your doctor when prescribing treatment for some conditions.

Another critically important reason to know your blood type is so that you are able to help others who need blood. When you give blood to a blood bank, the facility may sometimes send out a notice for a specific blood type, such as when a large car accident has occurred in your area. This information is vital to get the right type of blood quickly.

Whether you are in need of blood, or are willing to donate your blood to others, knowing your blood type is critically important. It may also save your life in a serious health crisis.


Erin shows overscheduled, overwhelmed women how to do less so that they can achieve more. Traditional productivity books—written by men—barely touch the tangle of cultural pressures that women feel when facing down a to-do list. How to Get Sh*t Done will teach you how to zero in on the three areas of your life where you want to excel, and then it will show you how to off-load, outsource, or just stop giving a damn about the rest.