What to Know About Total Iron-Binding Capacity (TIBC) Test

Medically Reviewed by Zilpah Sheikh, MD on September 20, 2023
4 min read

Your doctor might order a TIBC as part of an iron deficiency test. Here’s what to know about a TIBC test.  

A total iron-binding capacity test is a blood test that tells you how much transferrin in your blood is binding to iron, which tells you how well iron is functioning in your body. 

Your liver makes a protein called transferrin that attaches to, or binds to, iron in your blood. Once iron is bound to transferrin, it goes to your bone marrow to make red blood cells and hemoglobin, a protein that helps carry oxygen. 

There are two types of iron-binding capacity: unsaturated iron-binding capacity and total iron-binding capacity.

Unsaturated iron-binding capacity (UIBC). This measures how much transferrin is not yet bound to iron

Total iron-binding capacity (TIBC). This is the total amount of iron in your blood plus the UIBC. 

Iron is a key mineral for your health, but you lose iron through sweat, period blood, and when you shed skin and blood cells. Your body doesn’t really have a way to stop iron loss, so it tightly controls how it's absorbed.

Not enough iron can make you sick, but too much is also dangerous. Your body will deposit extra iron in your heart, liver, brain, and endocrine glands like your thyroid. This will damage your organs and can lead to heart failure and brain damage. 

Your doctor will order a TIBC test if you have signs of high or low iron. These symptoms include:

Too much iron can cause:

Your doctor might also check your TIBC during pregnancy, as you need more iron during this time. 

A TIBC blood test is usually done as part of an iron panel that includes iron and transferrin. Since transferrin and TIBC tests both measure the amount of transferrin, these are basically the same thing. In some cases, your doctor might order one or the other. 

They might also order other common tests along with iron-binding capacity tests, including tests measuring:

A TIBC test is a simple blood test, so there are very few risks. You might feel some discomfort or feel lightheaded and faint. These symptoms will pass, and you will be able to return to your normal activities shortly after having your blood drawn

Normal iron levels depend on your age, health history, and how the test was performed. Men, women, and children have different normal iron values. These are:

  • 50 to 20 micrograms per deciliter for children
  • 50 to 170 micrograms per deciliter for women
  • 65 to 175 micrograms per deciliter for men
  • TIBC: 255 micrograms per deciliter to 450 micrograms per deciliter for men and women
  • Transferrin saturation: 20 percent to 50 percent

Normal TIBC ranges can vary by lab and region. Ask your doctor about your test results.

Low TIBC means that you don’t have very much transferrin available to bind to iron. In other words, you have high iron levels, so most of the transferrin is bound to it, which leaves very little free in your blood. 

Some diseases can cause high levels of iron, including:

  • Iron poisoning
  • Lead poisoning
  • Cirrhosis, scarring in your liver
  • Hemochromatosis, a hereditary disease where you absorb too much iron from your food
  • Frequent blood transfusions for thalassemia that cause iron overload
  • Hemolytic anemia where your red blood cells die

High TIBC means that you have low levels of iron. When there isn’t much iron to attach to, you’ll have a lot of free transferrin in your blood.

Low iron levels can lead to iron deficiency anemia, a condition in which your body doesn’t have enough iron to make healthy red blood cells. This can be caused by:

Some substances and medications can affect your TIBC results. These include:

You can have lower iron levels when have your period, which can also affect your results. Talk to your doctor about how to prepare for a TIBC test and about any supplements, herbs, medications, or vitamins you’re taking.