Quantitative determination of unsaturated iron binding capacity in the blood can also be done with this test. So there are two types of iron binding capacity tests. Total iron binding capacity (TIBC) and unsaturated iron binding capacity (UIBC). The UIBC test measures how much of the transferrin does not bind iron, while the TIBC additionally measures the total amount of iron in the blood.

TIBC and UIBC

Iron is an element used to carry oxygen by binding to hemoglobin in the blood. There are also similar proteins, such as transferrin, to which iron binds during transport and other metabolic stages. Total iron binding capacity measures the capacity of iron to bind and transport iron with transferrin in the blood. Quantitative determination of unsaturated iron binding capacity in the blood can also be done with this test. So there are two types of iron binding capacity tests. Total iron binding capacity (TIBC) and unsaturated iron binding capacity (UIBC). The UIBC test measures how much of the transferrin does not bind iron, while the TIBC additionally measures the total amount of iron in the blood.

Transferrin is produced in the liver and is used to bind iron and transport it to where it is needed. The most important of these is transport to erythrocytes and bone marrow.



The TIBC test is used in the evaluation of various iron disorders. It indicates the maximum capacity of iron-binding proteins in blood serum to bind iron. The TIBC test shows disturbances in various stages of iron metabolism. Increasing capacity usually refers to vacant positions where iron can be bonded but not bonded. While iron binding capacity increases in iron metabolism disorders, it is expected to decrease in inflammatory diseases and malignancies. The decrease in iron in the blood in infectious diseases is one of the body’s defense mechanisms.

In the tests performed from the blood sample in the morning hours, the closest result is obtained. In the tests taken at other hours, there may be an error of up to 30%. In addition, disintegration of blood by hemolysis as a result of improper storage may adversely affect the test result.

Iron plays a role in the transport of oxygen in the human body mainly due to its ability to exchange electrons. It is also involved in energy production, DNA synthesis, RNA synthesis, and synthesis of proteins. It is even necessary for the structure and function of many enzymes.

60-70% of the iron in our body is in hemoglobin and circulating erythrocytes, 10% is in myoglobin and cytochromes and iron-containing enzymes. The remaining 20-30% is stored in cells, mainly in the liver and reticuloendothelial system macrophages, to be used when needed.



The organism is tightly programmed to protect iron because of its benefits. There is no normal physiological mechanism that releases iron from the organism. With the epithelial cells shed from the gastrointestinal tract, there is no iron loss except in small amounts and bleeding. The systemic balance of this element, which is too toxic, is provided by the control of absorption. The excess of iron in the body can cause various diseases. In excess of iron, it can accumulate in the liver, brain and endocrine organs such as the thyroid gland. In advanced stages, it can lead to many diseases, including heart failure.

With TIBC height, it is understood that the iron is deficient in the blood and the capacity to bind increases. Symptoms such as fatigue, pallor of the skin, weakness in the body, frequent colds and frequent illness, and slow mental development can be seen in these patients. Some patients may also experience swelling of the tongue and cracks on the corners of the mouth.

Causes of TIBC elevation:

  • Iron deficiency anemia
  • Blood loss
  • Vegetarian or vegan diet
  • Celiac disease
  • Pregnancy

Low TIBC is when the iron level in the blood is too high and there is an excess of iron. These patients may experience fatigue, nausea, abdominal pain and joint pain.

Causes of low TIBC:

  • Iron poisoning
  • Lead poisoning
  • Cirrhosis or liver diseases
  • Hemochromatosis
  • Frequent blood transfusions for thalassemia causing iron overload
  • Hemolytic anemia in which your red blood cells die

Iron binding capacity is not evaluated alone when used to study the stages of iron metabolism in the blood. It is evaluated together with other iron parameters, complete blood count, erythrocyte counts and other whole blood parameters.

Normal TIBC values are 255-450 micrograms/dL. This value can sometimes vary according to different working standards in different laboratories.


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