The Iron Test checks your iron, total iron-binding capacity (TIBC), and ferritin, which help support a number of vital functions in your body. Iron is an important nutrient needed to form hemoglobin, the substance in red blood cells that carries oxygen from your lungs throughout your body for energy. TIBC is a measurement of how well your blood attaches itself to iron to move it around your body. Ferritin is a protein in the blood that contains iron and helps you understand how much iron your body is storing. If your iron results are higher or lower than normal, you and your healthcare provider can work together to determine the next steps.