Can Blood Type Actually Change?

Normally, your blood type is determined by your genes and doesn't change throughout your life. However, under very specific medical or pathological conditions, your blood type can indeed change or show different results in tests. There are mainly three reasons for this: 1. Allogeneic Bone Marrow Transplant (Primary Reason) If you undergo a bone marrow or hematopoietic stem cell transplant from a donor (not yourself) due to diseases like leukemia, and the donor's blood type is different from yours, your hematopoietic function will be taken over by the donor's cells after a successful transplant. About a few months after the transplant, your blood type will completely change to be identical to the donor's. 2. Genetic Chaos or Weakened Antigens Due to Disease Certain diseases (such as acute leukemia, some cancers, or severe bacterial infections) can affect the expression of antigens on the surface of red blood cells. This can cause the original blood type antigens to decrease, disappear, or undergo pathological changes (e.g., an O-type person temporarily testing positive for A-type antigens). In such cases, your blood type usually reverts to its original state after the disease is cured or hematopoietic function is restored. 3. Temporary Immunodeficiency or Massive Transfusion When the body's immunity is extremely low, leading to very low antibody titers in the serum, or when a large amount of mismatched blood is transfused in a short period due to trauma or surgery (e.g., massive transfusion of O-type blood in an emergency), the tested blood type might be interfered with, showing a 'false change.' However, this is a temporary phenomenon.