By Mark Kennan
Updated Mar 24, 2022

Understanding your blood type can be valuable for medical, travel, and family planning reasons. While you can’t determine your exact blood type with absolute certainty from your parents’ types alone, you can narrow down the possibilities by applying the basic principles of the ABO blood group system.

There are four ABO blood types: O, A, B, and AB. Type O is the universal donor, meaning it can be transfused to any recipient. Type AB is the universal receiver, capable of receiving any ABO blood type. These characteristics arise from the presence or absence of A and B antigens on the surface of red blood cells.

Step 1 – Set Up Your Table

Create a simple 2×2 table. The columns represent the maternal alleles, and the rows represent the paternal alleles.

Step 2 – Fill in the Columns with Maternal Alleles

If your mother’s blood type is A, she could carry either the AA or AO genotype. Place “A” in the first column and “O” in the second.

Step 3 – Fill in the Rows with Paternal Alleles

Similarly, if your father’s blood type is AB, his genotype is AB. Place “A” in the first row and “B” in the second.

Step 4 – Combine Alleles to Find Possible Genotypes

Each cell shows a potential genotype for you. In this example, the possibilities are AA, AO, AB, and BO.

Step 5 – Convert Genotypes to Phenotypes

Drop the silent “O” allele when it appears: AO becomes A, and BO becomes B. Therefore, your blood type could be A, B, or AB. Type O is not possible in this scenario.

Repeat the process for any combination of parental blood types to determine your potential blood type range.

For more detailed information on ABO genetics and blood transfusion compatibility, consult reputable medical resources such as the American Red Cross or the Centers for Disease Control and Prevention.