Total iron-binding capacity (TIBC) is a medical laboratory test that measures the blood's capacity to bind iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 with transferrin

Transferrin

Transferrins are iron-binding blood plasma glycoproteins that control the level of free iron in biological fluids. In humans, it is encoded by the TF gene.Transferrin is a glycoprotein that binds iron very tightly but reversibly...

. It is performed by drawing blood

Phlebotomy

Phlebotomy is the process of making an incision in a vein.It is associated with the following concepts:* Venipuncture, the practice of collecting venous blood samples* The main practice of a phlebotomist, an individual trained to draw blood...

 and measuring the maximum amount of iron that it can carry, which indirectly measures transferrin

Transferrin

Transferrins are iron-binding blood plasma glycoproteins that control the level of free iron in biological fluids. In humans, it is encoded by the TF gene.Transferrin is a glycoprotein that binds iron very tightly but reversibly...

 since transferrin is the most dynamic carrier. TIBC is less expensive than a direct measurement of transferrin.

The TIBC should not be confused with the UIBC, or "unsaturated iron binding capacity" ( and ). The UIBC is calculated by subtracting the serum iron from the TIBC.

Interpretation

Taken together with serum iron

Serum iron

Serum iron is a medical laboratory test that measures the amount of circulating iron that is bound to transferrin. Clinicians order this laboratory test when they are concerned about iron deficiency, which can cause anemia and other problems....

 and percent transferrin saturation clinicians usually perform this test when they are concerned about anemia

Anemia

Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...

, iron deficiency

Iron deficiency (medicine)

Iron deficiency is one of the most common of the nutritional deficiencies. Iron is present in all cells in the human body, and has several vital functions...

 or iron deficiency anemia

Iron deficiency anemia

Iron-deficiency anemia is a common anemia that occurs when iron loss occurs, and/or the dietary intake or absorption of iron is insufficient...

. However, because the liver

Liver

The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

 produces transferrin, alterations in function (such as cirrhosis

Cirrhosis

Cirrhosis is a consequence of chronic liver disease characterized by replacement of liver tissue by fibrosis, scar tissue and regenerative nodules , leading to loss of liver function...

, hepatitis

Hepatitis

Hepatitis is a medical condition defined by the inflammation of the liver and characterized by the presence of inflammatory cells in the tissue of the organ. The name is from the Greek hepar , the root being hepat- , meaning liver, and suffix -itis, meaning "inflammation"...

, or liver failure

Liver failure

Acute liver failure is the appearance of severe complications rapidly after the first signs of liver disease , and indicates that the liver has sustained severe damage . The complications are hepatic encephalopathy and impaired protein synthesis...

) must be considered when performing this test. It can also be an indirect test of liver function, but is rarely used for this purpose.

The percent transferrin saturation (i.e., the result of the formula of serum iron/TIBC x 100) can also be a useful indicator.

Condition	Serum iron Serum iron Serum iron is a medical laboratory test that measures the amount of circulating iron that is bound to transferrin. Clinicians order this laboratory test when they are concerned about iron deficiency, which can cause anemia and other problems....	Transferrin and TIBC	Percent transferrin saturation
iron deficiency anemia Iron deficiency anemia Iron-deficiency anemia is a common anemia that occurs when iron loss occurs, and/or the dietary intake or absorption of iron is insufficient...	Low	High. The liver Liver The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...  produces more transferrin, presumably attempting to maximize use of the little iron that is available.	Low, as there is insufficient iron.
anemia of chronic disease Anemia of chronic disease Anemia of chronic disease, also referred to as anemia of inflammatory response is a form of anemia seen in chronic illness, e.g. from chronic infection, chronic immune activation, or malignancy...	Low, as the body holds iron intracellularly with ferritin Ferritin Ferritin is a ubiquitous intracellular protein that stores iron and releases it in a controlled fashion. The amount of ferritin stored reflects the amount of iron stored. The protein is produced by almost all living organisms, including bacteria, algae and higher plants, and animals... .	Low. The body produces less transferrin (but more ferritin), presumably to keep iron away from pathogen Pathogen A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host... s that require it for their metabolism. This is mainly regulated by increased hepcidin Hepcidin Hepcidin is a peptide hormone produced by the liver. It was discovered in 2000, and appears to be the master regulator of iron homeostasis in humans and other mammals. In humans, HAMP is the gene that encodes for hepcidin.-Structure:...  production.	Normal
pregnancy Pregnancy Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...  or use of hormonal contraception Hormonal contraception Hormonal contraception refers to birth control methods that act on the endocrine system. Almost all methods are composed of steroid hormones, although in India one selective estrogen receptor modulator is marketed as a contraceptive. The original hormonal method—the combined oral contraceptive... , but without iron deficiency	Normal	High. The liver increases the production of transferrin, thus raising TIBC.	Low, as there is excess transferrin with normal serum iron levels.

These examples demonstrate that to properly understand a value for TIBC, one also must know the serum iron, the percent transferrin saturation, and the individual clinical situation.

Usual values

Normal reference ranges are:

• Serum iron
  Serum iron
  Serum iron is a medical laboratory test that measures the amount of circulating iron that is bound to transferrin. Clinicians order this laboratory test when they are concerned about iron deficiency, which can cause anemia and other problems....
  
  : Male 65–177 μg/dL (11.6–31.7 μmol/L); Female 50–170 μg/dL (9.0–30.4 μmol/L)
• TIBC: 250–370 μg/dL (45-66 μmol/L)
• Transferrin saturation
  Transferrin saturation
  Transferrin saturation, abbreviated as TSAT and measured as a percentage, is a medical laboratory value. It is the ratio of serum iron and total iron-binding capacity, multiplied by 100. Of the transferrin that is available to bind iron, this value tells a clinician how much serum iron is actually...
  
  : Male 20–50%; Female 15–50%
• Serum ferritin: Male 20-250 μg/L, Female 15-150 μg/L

μg/dL = micrograms per deciliter; μmol/L = micromoles per litre.

Laboratories often use different units and "normal" may vary by population and the lab techniques used. Look at the individual laboratory reference values to interpret a specific test (for instance, your own).