What medical condition is characterized by a lack of iron?

Anemia is the condition characterized by a lack of iron, particularly iron-deficiency anemia, which is one of the most common types. Iron is essential for the body to produce hemoglobin, the protein in red blood cells that carries oxygen. When there is insufficient iron, the body cannot produce enough healthy red blood cells, leading to fatigue, weakness, and pale skin, among other symptoms.

The other medical conditions listed do not primarily involve iron deficiency. Hemophilia is a genetic disorder affecting blood clotting, leukemia is a type of cancer affecting blood and bone marrow, and diabetes is a metabolic disorder that affects how the body processes blood sugar. Therefore, anemia directly correlates to a lack of iron, making it the correct response for this question.