Studies Suggest These 3 Blood Types May Be Linked to a Higher Risk of Certain Cancers

Your blood type is something you're born with and usually think about only when donating blood or receiving a transfusion. But researchers have spent decades investigating whether the ABO blood group system may also be associated with the risk of developing certain diseases—including some forms of cancer.

Several large studies and meta-analyses have found that people with non-O blood types—A, B, and AB—may have a higher risk of certain cancers compared with people with blood type O. However, this does not mean that having one of these blood types causes cancer or that someone with type O is protected from cancer.

So, what does the research actually show?

1. Blood Type A

Among the ABO blood groups, type A has been one of the most consistently studied in relation to cancer risk.

A large systematic review and meta-analysis involving 89 studies and more than 100,000 cancer cases found that people with blood type A had a modestly higher overall cancer risk than people in non-A groups. The strongest associations included gastric (stomach) cancer and pancreatic cancer.

Another large meta-analysis published in 2023 examined 127 publications involving approximately 20 million participants. It found that blood type A was associated with increased risks of several cancers, including stomach and pancreatic cancers.

The association with stomach cancer has also been investigated specifically. A study combining genetic data with a meta-analysis of 40 studies found that, compared with blood type O, type A was associated with about a 19% higher risk of gastric cancer.

That sounds alarming, but an important point is that these are relative associations, not predictions that an individual person will develop cancer.

2. Blood Type B

Blood type B has also appeared in research examining cancer risk, particularly pancreatic cancer.

A large review published in 2023 found that blood type B was associated with a higher risk of pancreatic cancer compared with blood type O. The reported association was smaller than that observed for some other comparisons, but it was statistically significant in the analysis.

Earlier research that pooled 24 studies also found that B and AB blood groups were associated with higher pancreatic cancer risk in some populations, although the strength of the association differed depending on geographic and population characteristics.

This is an important reminder that research findings are not always identical across populations. Factors such as genetics, environment, infections, lifestyle, and study design can influence observed associations.

3. Blood Type AB

Blood type AB is less common than A, B, or O, but researchers have also identified associations between AB blood type and certain cancers.

In the large 2023 meta-analysis, AB blood type was associated with increased risks of stomach, pancreatic, and ovarian cancers compared with blood type O.

Research focusing specifically on gastric cancer also found that both A and AB blood groups were associated with a modestly increased risk compared with blood type O.

Again, these findings describe a statistical association across groups, not a diagnosis or a certainty for any particular individual.

Why Might Blood Type Be Linked to Cancer?

Researchers don't yet have a complete explanation.

One possibility involves the biological molecules known as ABO blood-group antigens, which are found on the surface of red blood cells and other cells in the body. These molecules may influence processes such as inflammation, cell adhesion, immune responses, and interactions between cells.

For stomach cancer, researchers have also investigated possible interactions between ABO blood groups and Helicobacter pylori, a bacterium associated with stomach ulcers and stomach cancer.

However, scientists have not established a single mechanism that explains all of the observed relationships. More research is needed.

What About Blood Type O?

Interestingly, many studies have found that people with blood type O tend to have a lower risk of some cancers, particularly pancreatic and gastric cancers, compared with people with non-O blood types.

A 2014 systematic review found that blood type O was associated with a lower risk of several cancers, including pancreatic and gastric cancer.

A more recent umbrella review of systematic reviews also found evidence supporting an association between blood type O and lower gastric cancer risk, while finding higher pancreatic cancer risk among several non-O groups.

But there is an important caveat: lower statistical risk does not mean zero risk.

People with blood type O can still develop pancreatic, stomach, breast, colorectal, lung, and other cancers.

Does Having A, B, or AB Mean You Will Get Cancer?

Absolutely not.

This is perhaps the most important point.

Blood type is only one potential factor among many. Cancer development is complex and can involve genetics, age, smoking, alcohol consumption, obesity, infections, environmental exposures, family history, and many other factors.

For example, established risk factors for stomach cancer include H. pylori infection, smoking, certain dietary factors, and other medical and genetic factors. Blood type should therefore not be viewed as a stand-alone predictor of whether someone will develop cancer.

The studies discussed above primarily demonstrate associations, meaning that certain blood groups occur more or less frequently among people with particular cancers. They do not prove that the blood type itself directly causes the cancer.

What Should You Do If You Have Type A, B, or AB?

There is no recommended cancer treatment or preventive medication simply because someone has a particular ABO blood type.

Instead, focus on the risk factors you can actually influence.

That includes:

• Avoiding tobacco products
• Limiting alcohol consumption
• Maintaining a healthy weight
• Eating a balanced diet rich in vegetables, fruits, whole grains, and other nutrient-dense foods
• Staying physically active
• Following recommended cancer screening guidelines for your age and risk level
• Discussing significant family cancer history with a healthcare professional
• Seeking medical evaluation for persistent or unusual symptoms

If you know your blood type is A, B, or AB, there is no reason to panic. These findings are useful for researchers because they may help uncover biological pathways involved in cancer, but they are not a prediction of your personal future.

The Bottom Line

Research has found intriguing associations between the ABO blood group system and certain cancers.

Blood types A, B, and AB have each been linked in studies to increased risks of at least some cancers, particularly cancers involving the digestive system. Blood type A has shown one of the most consistent associations with stomach and pancreatic cancer, while B and AB have also been linked to pancreatic cancer in several analyses.

But your blood type is not a cancer diagnosis—and it should never be used to predict that you will develop cancer.

If anything, these findings highlight why researchers continue to study the relationship between genetics, blood-group biology, and disease.

Knowing your blood type can be interesting. Knowing and managing your actual cancer risk factors is far more important.

Sources

• PubMed — ABO blood groups and risk of cancer: a systematic review and meta-analysis
• PubMed — Epidemiological and genetic evidence for the relationship between ABO blood group and human cancer
• BMC Cancer / PubMed — Blood groups A and AB are associated with increased gastric cancer risk
• American Journal of Epidemiology / PubMed — ABO blood group and risk of pancreatic cancer
• BMC Medicine — ABO and Rhesus blood groups and multiple health outcomes: umbrella review
• PubMed — 2025 systematic review and meta-analysis of ABO blood groups and pancreatic cancer outcomes