Knowing your blood type could do more than help in emergencies—it may also offer insight into long-term health risks, including cancer.

A 2015 study suggested that individuals with Type O blood may have a reduced risk of developing certain cancers, including stomach, pancreatic, and colorectal cancer. In contrast, people with A, B, or AB blood types were found to have a higher risk, particularly for stomach and pancreatic cancers.

Type O has also been linked to a lower risk of heart disease, possibly due to fewer clotting factors in the blood. However, researchers stress that while blood type may influence risk, it does not affect cancer mortality rates.

Most people learn their blood type only during medical treatment. Each type—A, B, AB, or O—can be positive or negative, based on the presence of the Rh protein.

Experts caution that blood type is just one factor among many in cancer risk and prevention.