Skip to content
Blood Test Tracker

Total Iron-Binding Capacity (TIBC)

How much iron your blood's carrier protein, transferrin, could hold in total. It usually rises when iron stores are low.

AI-verified against cited sources. Awaiting expert reviewAlso called TIBCLOINC 2500-7

Check your result

Sex (optional)

Type your result to see where it falls.

Nothing you type here leaves your browser.

What it is

TIBC stands for total iron-binding capacity. Iron travels in your blood attached to a protein called transferrin, and TIBC shows how much iron all the transferrin in a blood sample could carry if it were completely full. It is usually reported with serum iron, and together the two give transferrin saturation. UIBC is the part of the capacity that isn't in use, which is TIBC minus iron.

Why it matters

When iron stores run low, the liver makes more transferrin, so TIBC tends to go up. TIBC tends to be low in inflammation, liver disease and low protein states. That pattern helps your clinician tell iron deficiency from anemia caused by long-term illness. TIBC doesn't diagnose anything on its own, so it is read with serum iron, transferrin saturation and ferritin.

If it’s low

A low TIBC means there is less transferrin than usual in your blood. This often reflects inflammation, low protein levels or liver disease. It can also be slightly low when the body holds too much iron.

Common causes

  • Inflammation or infection
  • Liver disease, such as cirrhosis
  • Low protein levels from malnutrition or from protein loss through the kidneys
  • Hemolytic anemia, where red blood cells break down early
  • Iron overload conditions, including the inherited condition hemochromatosis
  • Sickle cell anemia

What can help

  • Ask whether CRP, albumin or liver tests would help explain it
  • Ask your clinician to read it together with serum iron, transferrin saturation and ferritin

If it’s high

A high TIBC most often fits with low iron stores. It can also be higher during pregnancy or in people taking estrogen-containing birth control, where it does not mean low iron.

Common causes

  • Iron deficiency (low iron stores)
  • Pregnancy, especially late pregnancy
  • Estrogen-containing birth control pills
  • Heavy periods or other ongoing blood loss
  • Not enough iron in the diet

What can help

  • Ask your clinician to read it together with ferritin and transferrin saturation
  • If iron stores are low, ask about the cause and whether iron treatment is right for you
  • Eat iron-rich foods such as meat, fish, beans, lentils and fortified cereals

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

The usual range depends on age. Choose an age to see the one that applies.

Children and teens 2 ranges

See TIBC by age and sex, with the U.S. survey numbers where they exist.

If this applies to you

TIBC means a little more for some people. Open the one that fits you.

Low iron or anemia

TIBC tends to rise when iron runs low. BSG lists a raised TIBC, along with low ferritin, low transferrin saturation and low serum iron, among the blood signs of iron deficiency.

Blood tests for low iron and anemia

How common is your level?

NHANES describes the US civilian, non-institutionalized population, not a 'healthy' reference group. People with disease, on medication, fasting or not (except fasting-subsample markers), smokers and so on are all included. A percentile says where a value sits among Americans of that sex and age, not whether it is normal.

How TIBC varies with age in the U.S.Shaded: middle 90% and middle 50% of people. Line: the median. µg/dL. Point at any age, or focus the chart and use the arrow keys, to read both sexes in words.

Use the left and right arrow keys to read each age. Shift moves five years.

Reference data derived from CDC/NCHS National Health and Nutrition Examination Survey (NHANES), cycles 2017-March 2020 (pre-pandemic). Analysis by bloodtesttracker.com; not endorsed by CDC, NCHS or HHS.

Explore TIBC by age and sex: every percentile as a table, with a download.

What can affect your result

  • Pregnancy and estrogen-containing birth control raise TIBC
  • Inflammation, infection, liver disease and low protein levels lower it
  • How the lab gets the number: measured directly, or calculated from iron plus UIBC or from transferrin
  • Age: ranges for babies and children differ from adults
  • The tube type: EDTA plasma can give wrong results
  • Iron treatment or a transfusion shortly before the draw
  • Estrogen-containing birth control and pregnancy raise TIBC and transferrin, usually with normal transferrin saturation (Labcorp).
  • Inflammation, infection, liver disease and low protein levels lower TIBC.
  • EDTA plasma and gross hemolysis can give wrong results. Labs need serum or lithium heparin plasma.
  • Labcorp asks that the sample be drawn before iron treatment and that iron testing wait at least four days after a blood transfusion.
  • Some labs measure TIBC directly, while others calculate it from iron plus UIBC or estimate it from transferrin, so numbers can differ slightly between labs.

Morning, because it is usually drawn with serum iron. Changes over weeks as iron stores change. It does not swing from meal to meal the way serum iron does.

When to talk to a clinician

A TIBC result on its own is rarely urgent. Talk with a clinician if it is outside your lab's range together with tiredness, shortness of breath, or a low blood count, ferritin or serum iron.

Questions you could ask

  • How do my iron, TIBC and transferrin saturation fit together?
  • Could pregnancy, birth control or low iron explain a high TIBC?
  • Should we check ferritin and transferrin saturation too?
  • Could inflammation or a liver or protein problem explain a low TIBC?
  • Should we look at CRP, albumin or liver tests?

Questions people ask

What is the difference between TIBC, UIBC and transferrin?

Transferrin is the carrier protein itself. TIBC is how much iron it could carry in total. UIBC is the unused part, which is TIBC minus serum iron. Some labs report transferrin instead of TIBC.

Why is my TIBC high when my iron is normal?

TIBC reflects how much transferrin you have, and that rises when iron stores are low, in pregnancy, and with estrogen-containing birth control. Labcorp notes that with birth control, TIBC and transferrin are higher but saturation stays normal. Ferritin and transferrin saturation help sort out which it is.

Do I need to fast for a TIBC test?

MedlinePlus advises not eating or drinking for 8 hours before this test, mainly because it is usually drawn with serum iron. Follow your lab's instructions.

How do I convert TIBC units?

Multiply µg/dL by 0.179 to get µmol/L. To go the other way, multiply µmol/L by 5.585. For example, 300 µg/dL is about 53.7 µmol/L.

Show the science and sources

Units

  • 1 µg/dL = 1 µg/dL
  • 1 µg/dL = 0.1791 µmol/L

Open the TIBC unit converter

For clinicians and researchers

TIBC equals serum iron plus UIBC. Labs measure it directly, calculate it as iron plus UIBC, or estimate it from transferrin. The AASLD guideline notes that some labs calculate it from iron plus UIBC and others from transferrin, so values are not always interchangeable. Labcorp and ARUP use colorimetric or spectrophotometric methods. TIBC rises in iron deficiency, in pregnancy and with oral contraceptives (with normal saturation), and falls with hypoproteinemia, inflammation, liver disease and hemochromatosis. Labcorp notes that TIBC is less useful in iron poisoning than previously believed. Reference intervals: 250–450 µg/dL at Labcorp (all ages) and 240–450 µg/dL at ARUP (age 18 and over); ARUP lists 59–175 µg/dL for 0–2 months and 250–400 µg/dL for 3 months to 17 years. MedlinePlus quotes wider, sex-specific intervals (men 171–505 µg/dL, women 149–492 µg/dL). The SI factor is 1 µmol/L = 5.585 µg/dL.

LOINC 2500-7 (primary), 14800-7, 35215-3. Specimen: serum-or-plasma.

Sources

  1. Iron and Total Iron-binding Capacity (TIBC) (test 001321), Labcorp
  2. Iron and TIBC sample report (test 001321), Labcorp
  3. Pediatric Testing Reference Ranges, Labcorp (2022)
  4. Iron and Iron Binding Capacity (test 0020420), ARUP Laboratories
  5. Total iron binding capacity, MedlinePlus Medical Encyclopedia (NIH)
  6. Diagnosis and management of hemochromatosis: 2011 practice guideline by the American Association for the Study of Liver Diseases, Hepatology (2011)
  7. Iron (compound summary, CID 23925), PubChem (NIH)
  8. SI Conversion Calculator (AMA Manual of Style), American Medical Association / Oxford University Press

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

Calculators

Related markers