Hemoglobin is a protein that uses iron to carry oxygen throughout our body. When children do not get enough iron in their diet, the body cannot make hemoglobin, which means that less oxygen reaches cells and tissues and affects how the body works. In young children, iron is important because it plays a role in muscle function, energy creation and brain development. Children who develop iron-deficiency anemia can develop learning and behavioral problems. As a public health program, WIC is required to check hemoglobin levels to help prevent iron-deficiency anemia.