The hemoglobin E trait is the presence of an abnormal type of the oxygen-carrying substance in red blood cells (hemoglobin) called hemoglobin E. Because people who have hemoglobin E trait also have some normal hemoglobin (hemoglobin A), they rarely have problems from the condition but can pass on the trait to their children.

If a person inherits hemoglobin E from both parents, he or she has no normal hemoglobin (hemoglobin A) and has what is called hemoglobin EE, in which the red blood cells are smaller than normal. A person who has hemoglobin E with little or no normal hemoglobin may have mild anemia.