Total iron-binding capacity (TIBC)
Measure of how much iron transferrin and other blood proteins can bind
Also known as
Definition
Total iron-binding capacity (TIBC) shows how much iron the transport proteins in the blood, mainly transferrin, can bind. In the blood, iron is carried to the tissues bound to transferrin. TIBC is usually measured together with serum iron, transferrin and ferritin to assess iron status. The same report often also lists iron or transferrin saturation.
| Parameter | Value |
|---|---|
| Unit | µg/dL (µmol/L) |
| Reference Range | Typical range for adults: men 171–505 µg/dL (approx. 30.6–90.4 µmol/L), women 149–492 µg/dL (approx. 26.7–88.1 µmol/L). Labs may differ; the reference range in your own report is what counts. Discuss your results with your doctor. |
Agree on your personal target range with your doctor.
Conversion: µg/dL × 0.179 = µmol/L (molar mass of iron 55.85 g/mol).
↓ What a low value means
A low TIBC may be linked to low protein levels in the blood, inflammation, liver disease such as cirrhosis, malnutrition or certain types of anemia, for example hemolytic anemia, pernicious anemia or sickle cell anemia. The value alone is not a diagnosis; your doctor reads it together with the other iron values and the blood count.
↑ What a high value means
TIBC is usually elevated when the body's iron stores are low, for example in iron deficiency anemia. It is also often higher in late pregnancy, and birth control pills can affect the value. Whether an elevated value points to iron deficiency only becomes clear in combination with ferritin, serum iron and the blood count; discuss this with your doctor.
When to test
Fasting is usually required: MedlinePlus mentions 8 hours (encyclopedia) or up to 12 hours (test page) without eating or drinking, and the test is often done in the morning. Some medicines, including ACTH, birth control pills and fluorides, can change the result; do not stop them on your own. The test is ordered for signs of anemia or when other values suggest iron deficiency.
Frequently asked questions
Why is TIBC often elevated in iron deficiency? +
According to MedlinePlus, TIBC is usually higher than normal when the body's iron stores are low. That is why it is read together with ferritin and serum iron: only the overall picture allows your doctor to interpret it.
Do I need to fast before the blood draw? +
Usually yes. MedlinePlus mentions 8 hours (encyclopedia) or up to 12 hours (test page) without eating or drinking; blood is often drawn in the morning because iron levels vary throughout the day. Follow the instructions of your practice or lab.
Which values make up iron status? +
Typically serum iron, transferrin, TIBC and ferritin. Depending on the question, hemoglobin, hematocrit, the complete blood count and mean corpuscular volume (MCV) are added.
Why do reference ranges differ between labs? +
Labs use different measurement methods and sometimes different samples, so normal ranges vary. Compare your values with the range in your own report.
Total iron-binding capacity (TIBC)
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.