Ferritin is the major protein found in the blood cells that stores iron. The Ferritin Blood test is used to check the iron levels in the body and may help diagnose various health conditions like iron-deficiency anemia, hemochromatosis (a condition where the body produces too much iron). Low ferritin levels in the blood show the presence of iron deficiency (anemia) in the body. The body requires iron to make hemoglobin, a protein found in red blood cells that helps transport oxygen from the lungs around the body.