Total iron binding capacity (TIBC) is a blood test that shows if there is too much or too little iron in the blood. Iron is carried in the blood attached to the protein transferrin. This test helps measure the ability of a protein called transferrin to carry iron in the blood.

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

You should not eat or drink for 8 hours before the test.

Make sure your doctor knows about all the medications you are taking. Some medicines can interfere with test results.

• Drugs that can raise TIBC include fluorides and birth control pills.
• Drugs that can lower TIBC include ACTH and chloramphenicol.

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

This test is usually done when the health care provider suspects low iron (deficiency) as a cause of anemia.

• Iron: 60-170 mcg/dL
• TIBC: 240-450 mcg/dL
• Transferrin saturation: 20-50%

Note: mcg/dl = micrograms per deciliter

TIBC is usually higher-than-normal when the body's iron stores are low. Higher-than-normal TIBC may mean:

• Iron deficiency anemia
• Pregnancy (late)

Lower-than-normal TIBC may mean:

• Cirrhosis
• Hemolytic anemia
• Hypoproteinemia
• Inflammation
• Liver disease
• Malnutrition
• Pernicious anemia
• Sickle cell anemia

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Ginder G. Microcytic and hypochromic anemias. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 163.