This test measures the amount of the protein transferrin in your blood.Your liver makes transferrin. When your bodys stores of iron run low, your liver makes more transferrin to get more iron into your blood. Iron plays many important roles in your body, including helping your red blood cells carry oxygen to the cells in your body. Nearly all the iron in your body is normally attached to transferrin.Normally, your body carefully keeps track of your iron level and tries to keep it from rising too high or falling too low.This test can give your healthcare provider more information about health issues like anemia that are affecting your bodys iron supply.