by
Almog Ramrajkar
| Apr 28, 2025
Updated on - 03 Feb 2026
Have you ever thought that your blood type, one of the essential traits that make you who you are, could ever change? For the majority of people, the answer is “no” because their blood type is a generic blueprint that is predetermined from birth. However, science identifies a few exceptional and life-saving medical circumstances in which this rule is altered.
This article explores whether blood type can change, the causes and rare medical conditions linked to it. You will also learn how blood transfusions can affect blood type and how to confirm a particular type accurately. First, let’s understand the different blood types.
What are blood groups?
The absence or presence of certain antigens on red blood cells determines blood type. The most well-known system is the ABO grouping, which includes types A, B, AB and O. Additionally, the Rh factor (positive or negative) further categorises each blood type into positive or negative.
Can your blood type change?
Most people's blood type stays the same from birth to death. It's determined by genetic inheritance, and there is no natural mechanism for the body to alter it. However, if you've ever wondered if your blood group can change, under exceptional medical conditions, some people experience a shift in their blood type.
What causes a change in blood type?
A change in blood type is the outcome of significant biological or medicinal processes rather than a natural occurrence. Here are some causes:
- Bone marrow transplant: A common reason for a change in blood type is a bone marrow transplant. Bone marrow produces blood cells, and if a person undergoes a transplant from a donor with a different blood type, the blood group changes to match the donor's. This process can take weeks or months.
- Massive blood transfusions: A temporary change can occur during enormous blood transfusions. If an individual loses a significant amount of blood and receives a large volume of transfused blood, their circulating blood may reflect the donated type for a short period. However, once their body replenishes its own blood supply, the original type returns.
- Bacterial infections: In extremely rare cases, bacterial infections can cause a temporary shift in blood type. Certain bacteria produce enzymes that can alter the molecular structure of blood group antigens. For instance, some intestinal infections have been known to convert type A blood into something resembling type B, a phenomenon called the "acquired B antigen." This condition is usually temporary and resolves once the infection is treated.
Rare medical conditions linked to blood type changes
The formation or expression of blood type antigen on red blood cells might be directly disrupted by some complicated or serious medical conditions, like:
- Haematological disorders (e.g., myelodysplastic syndrome, leukaemia): Disorders that affect bone marrow function or blood cell development can lead to weaker or absent A, B or H antigens on red blood cells. This occurs when abnormal or immature blood cells replace healthy ones, disrupting normal antigen formation.
- Acquired weak or mixed ABO subgroups: Some cancers and infections can cause the temporary appearance of weak or mixed blood group expressions, known as “acquired A or B subgroups.” These changes are usually reversible once the underlying condition is treated.
- Paroxysmal nocturnal haemoglobinuria (PNH): PNH is a rare acquired stem cell disorder in which red blood cells lack certain surface proteins, leading to their premature destruction. Although it mainly affects other red-cell markers rather than ABO antigens, it can complicate blood typing in some cases.
How blood transfusions and bone marrow transplants affect blood type
Due to the huge volume of donor cells in circulation, a major blood transfusion may momentarily cause your blood type to change, but this effect eventually disappears as your body replaces the donor cells with your original kind.
On the other hand, a bone marrow or haematopoietic stem cell transplant may result in a long-lasting alteration. If a person with blood type A receives a transplant from a type O donor, the new healthy bone marrow will start making red blood cells that carry the donor’s type O blood antigen. The recipient's whole blood system gradually changes to match the donor’s type.
Can pregnancy alter your blood type?
The mother’s core blood types (ABO and RH) are not altered during pregnancy. Rh antibodies, however, can form in a Rh-negative mother bearing a Rh-positive child. The mother’s immune system creates antibodies if the baby’s Rh-positive blood gets into her system because it perceives the Rh factor as alien. The mother’s innate Rh-negative status is unaffected; however, this is controlled by injections like RhoGAM to avoid difficulties for the present and future pregnancies.
How to confirm your blood type accurately?
The most accurate way to confirm your blood type is through professional medical testing. While at-home kits are available, their results may not always be reliable. You can learn your blood type through blood donation, as blood banks provide validated reports. Pregnant women are also routinely tested to check for Rh incompatibility with the baby.
Before any surgery or blood transfusion, hospitals perform a Type and Screen test to identify the patient’s blood group. Alternatively, you can request an ABO and Rh typing test at a certified medical laboratory for a precise result.
Why blood type awareness matters for health insurance coverage
Generally, your blood type won't impact your health insurance policy, but it is important to know about the health concerns associated with your blood type. For example, some blood types may have an increased or decreased risk of various illnesses or blood clots. Being aware of your particular type promotes proactive health monitoring.
Furthermore, having comprehensive health insurance is important to make sure that you are financially covered for medical emergencies. It becomes more vital for illnesses or injuries that require complicated interventions like transfusions or life-saving transplants. In such cases, having a critical illness insurance plan can be particularly valuable, as it offers a lump-sum payout to cover the high costs of serious illnesses like heart attacks, strokes or cancer.
If you want personalised guidance on health insurance and help choosing the plan that suits your needs best, fill out the form on this page. Our team will get in touch to help you make the right choice.
Conclusion
Blood type changes are extremely rare, and for most people, their blood type remains the same throughout life, except in rare cases linked to severe illnesses or treatments. Knowing your blood type is an important part of being prepared for emergencies, especially situations that may require transfusions or hospital care. That’s why having a reliable health insurance plan is equally important. It ensures that when unexpected medical issues arise, you have access to quality treatment without stressing about finances.
FAQs
1. Can lifestyle factors like diet or exercise affect my blood type?
No! Because your blood type is established through genetics, dietary changes, exercise routines or supplementation cannot affect your blood type.
2. What is the "Bombay Phenotype”?
The Bombay phenotype is a very uncommon blood type that does not have the H antigen, a precursor to A or B antigens. Initial blood typing may appear to be Type O due to clear inherited, genetic differences that complicate transfusions, rather than a change.
3. If blood type changes after a bone marrow transplant, is it permanent?
Yes, the recipient's blood-forming cells are permanently replaced after a successful bone marrow transplant. The receiver will experience a long-lasting shift since the new cells created by the bone marrow will carry the donor’s blood type.
Disclaimer: The information provided in this blog is for educational and informational purposes only. It is not intended as a substitute for professional advice, diagnosis or treatment. Please consult a certified medical and/or nutrition professional for any questions. Relying on any information provided in this blog is solely at your own risk, and ICICI Lombard is not responsible for any effects or consequences resulting from the use of the information shared.