Experts do not yet know what causes leukemia.

A risk factor is anything that raises your chance of getting a disease. Risk factors for some types of leukemia include:

• Smoking and tobacco use.
• Being exposed to large amounts of radiation.
• Being exposed to certain chemicals in the workplace.
• Past chemotherapy or radiation for another cancer. (This is rare, and not all chemotherapies raise your leukemia risk.)

Most people who get leukemia do not have any risk factors.

Most types of leukemia do not seem to run in families, but in some cases, chronic lymphocytic leukemia (CLL) does.¹ There are also certain genetic conditions, like Down syndrome, that can make acute myelogenous leukemia (AML) more likely.