An iron saturation test measures the body's ability to bind iron and transport it to necessary sites, such as the liver and bone marrow, according to the Iron Disorders Institute. These tests usually express measurements as transferrin-iron saturation percentages.
Transferrin is a protein that can bind two iron atoms and transport them through the blood, explains the Iron Disorders Institute. A fasting transferrin-iron saturation percentage greater than 45 percent is indicative of iron loading, or the accumulation of iron in the body. A low iron saturation could be indicative of anemia, especially if it is present in conjunction with other iron-deficiency symptoms, according to the American Society of Hematology.