Why It’s Important to Know Your Blood Type

Understanding Blood Transfusions

Blood is made up of different components: red blood cells, white blood cells, plasma, and platelets. It has the responsibility of transporting oxygen, nutrients, and proteins throughout our body in addition to performing other vital functions. However, there are various different blood types that are individually unique.

What is a Blood Type?

We all have blood flowing through our blood vessels, but not all blood is identical. A person’s blood type determines who they can receive blood from, and who they can donate blood to. There are in total, eight different blood types: A+, A-, B+, B-, AB+, AB-, O+, and O-.

An antigen is a substance that causes an immune system response. The presence or absence of two antigens, A and B, on the surface of red blood cells is what determines a person’s blood type; however, there are also multiple minor blood group antigens. Along with either the presence or absence of a third antigen, the Rh factor (a protein), is responsible for a blood type being either positive or negative (Rh positive or Rh negative).

Understanding Blood Transfusions

There is a specific guideline in which blood transfusions must be conducted in order to be safe and successful. Transfusions must be matched appropriately to avoid dangerous outcomes. The breakdown is as follows:

  • Type A+ can donate only to A+ and AB+; can only receive from A+, A-, O+, and O-
  • Type A- can donate only to A+, A-, AB+, and AB-; can only receive from A- and O-
  • Type B+ can donate only to B+ and AB+; can only receive from B+, B-, O+, and O-
  • Type B- can donate only donate to types B+, B-, AB+, and AB-; can only receive from B- and O-
  • Type AB+ can only donate to AB+; can receive from all blood types
  • Type AB- can donate only to AB+ and AB-; can only receive from A-, B-, AB-, and O-
  • Type O+ can only donate to blood types A+, B+, AB+, and O+; can only receive from O+ and O-
  • Type O- can donate to all blood types. It is known as the universal donor type; can only receive from O-

Receiving the wrong blood transfusion can be disastrous – and even deadly.

If a person receives an incompatible blood type during a transfusion, the immune system of the person receiving the transfusion goes into a massive activation and attacks the invading blood. Clotting may occur, resulting in complications such as kidney failure, circulatory failure, shock, or possibly, even death. So it is very important that blood types are always correctly labelled.

Additionally, most people aren’t aware that there are a few different types of blood donations a person can give. “Whole blood” donations are the most common kind of donations, and are the kind most people are familiar with. However, there are other types of blood donations as well:double red cells, platelets, and plasma donations, in which each different type serves a specific purpose. For example, platelet apheresis donations (apheresis is the process of only collecting one component in blood during a blood donation by an apheresis machine), in which only platelets are collected, are crucial in cancer and organ transplant treatments.


One segment of the population that must always know their blood type is pregnant women, in order to determine the baby’s Rh factor because an incompatible Rh factor with a baby in the womb can lead to certain medical problems. Arguably, the most important reason for knowing your blood type is in the event of a medical emergency, where you may be in need of a blood transfusion. Although your blood type will be checked upon receiving blood, it is definitely important for you to know your own blood type in case of any confusion or human error which may occur – or on the other end, during a nationwide emergency, for example, when people are in need of blood donations and you choose to become a donor yourself. Emergency response services often announce which blood type they have a shortage of, and it may likely be yours. Remember that this personal bit of knowledge will be beneficial in many ways, whether in times of helping others in need or in protecting yourself from potential harm.


By Dr . Harit Suwanrusme , Hematologist, Horizon Cancer Center, Bumrungrad Hospital

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Posted by Bumrungrad International