Total Iron Binding Capacity (TIBC)

You get iron from eating food or taking supplements. There are iron-only supplements, but many multivitamin/mineral supplements also contain iron. Most people in the United States get enough iron. However, certain people may be more likely to have trouble getting enough iron. Iron levels that are too low or too high can cause health concerns. Not having enough iron is the most common cause of anemia.

There are different types of iron tests, including a serum iron test, transferrin test, total iron-binding capacity (TIBC) test, and ferritin blood test. Most of the iron in your blood is carried by a protein called transferrin. A serum iron test measures the iron currently attached to transferrin, while TIBC reflects how much iron transferrin could carry if it were fully loaded, giving an indirect picture of how much transferrin is in your blood. Comparing these two values shows what percentage of transferrin is actually saturated with iron, which is typically low when iron is in short supply and high when iron is being stored in excess. The amount of iron in your blood varies throughout the day and may be higher in the morning.

You may need testing if you have symptoms of iron levels that are too low or too high. Symptoms of low iron include weakness or fatigue, dizziness, shortness of breath, and arrhythmia. Symptoms of high iron include weakness or fatigue, joint pain, abdominal pain, loss of interest in sex or erectile dysfunction, and skin color changes.

Your provider will consider your symptoms, age, medical history, and other blood test results to interpret iron tests.

A high TIBC means your blood has more capacity to bind iron than usual. This is the typical pattern in iron deficiency anemia, where the body makes more transferrin to try to grab whatever iron it can.

A low TIBC means your blood is binding less iron than usual. This is often seen in iron overload conditions like hemochromatosis, in long-term illness or inflammation (anemia of chronic disease), in liver disease, and in malnutrition.

Low iron levels may indicate iron deficiency anemia, another type of anemia, or thalassemia, an inherited blood disorder. TIBC results are also useful for telling apart low iron caused by true iron deficiency from low iron seen with chronic inflammation or certain other illnesses.

High iron levels may indicate hemochromatosis, lead poisoning, or liver disease.

Most conditions causing too little or too much iron can be treated with supplements, dietary changes, medicines, and other therapies.

Not all abnormal results indicate a medical condition needing treatment. Some medicines, including birth control pills and estrogen treatments, can affect iron levels.