Total Iron Binding Capacity (TIBC)

The Total Iron Binding Capacity (TIBC) is a tool for understanding how iron is utilized in the body after absorption.  This test assesses how much iron is bound to transferrin, the protein that transports iron throughout the body. 

TIBC Testing

Total iron-binding capacity (TIBC) measures the amount of total binding proteins and their capacity to bind to serum iron in the bloodstream. It is often used with other iron tests to assess the body’s iron status in an iron and TIBC panel.

The body synthesizes transport proteins in relationship to a person’s need for iron. When iron storage is low, transport protein production increases. When iron storage is high, there is a reduction in the production of transport proteins. Transferrin is a transport protein responsible for 50% to 70% of all iron-binding. Generally, the TIBC is described as a measure of transferrin binding capacity because it is the primary transport protein. 

TIBC (µg/dL) = UIBC (µg/dL) + Iron (µg/dL)

TIBC in Pregnancy

Transferrin production steadily increases throughout pregnancy, almost doubling by the peak in the third trimester. This causes an elevation in the TIBC. More transferrin in the bloodstream means more of a capacity for iron-binding. 

TIBC remains elevated through at least six weeks postpartum. There is limited data on when these values return to normal and may be more associated with birth outcomes and blood loss in childbirth. 

High TIBC in Pregnancy

​TIBC is elevated when there is iron deficiency, as it represents a large portion of unbound transport proteins and lower serum iron levels. It can also represent an elevated production of transferrin and transport proteins. 

Most Common Causes of High TIBC in Pregnancy 

• Nutritional Deficiencies (iron, magnesium)
• Insulin Resistance
• Internal Bleeding
• IBD Flare (Crohn's Disease, Ulcerative Colitis)
• Hemolytic Anemia
• Hypothyroidism
• Heavy Metal Exposure
• Certain Medications (Oral Contraceptive Use at Conception)

Low TIBC in Pregnancy

​A low TIBC occurs when there is more than adequate iron in the bloodstream but the transport proteins have a reduced availability to bind additional iron. This can be due to iron excess or a reduced production of transferrin.

Most Common Causes of Low TIBC in Pregnancy

• Iron Overload/Hemochromatosis
• Low- Protein Diet
• Liver Disease/Inflammation
• Hemolysis
• Thalassemia
• Low Estrogen

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Medical Disclaimer:
This content is for educational purposes only and is intended for licensed medical professionals. It is based on current research, subject to change, and not intended to diagnose, treat, or prevent any medical condition. This information does not replace consultation with a qualified healthcare provider. Seek professional medical evaluation and treatment from a licensed provider. Use of this information is at your own risk.

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