G6PD deficiency occurs most often in men. It is rare in women.
The disorder is more common in people of African descent than whites. It affects about 1 in 10 African-American men in the U.S. It is also common in people from areas in the Mediterranean, Africa, Asia, and Middle East.
The severity of the disorder varies, depending on the group. In African Americans, the problem is mild. It mainly affects older red blood cells. In whites, the disorder is often more serious.