Unsaturated Iron-Binding Capacity (UIBC)

Total Iron-Binding Capacity (TIBC) measures the total capacity of transferrin to bind with iron in the blood. In contrast, the Unsaturated Iron-Binding Capacity (UIBC) only measures the portion of transferrin unbound by iron. It can be used with other iron indices to assess iron absorption and metabolism.

UIBC Testing

UIBC measures unsaturated transport proteins. It is used in conjunction with total serum iron to calculate the total iron-binding capacity (TIBC) and is part of an iron and TIBC panel.

TIBC (µg/dL) = UIBC (µg/dL) + Iron (µg/dL)
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The body makes transport proteins in response to iron levels. About 30% of transport proteins are used at any given time, and the UIBC measures the unbound transport protein content. 

UIBC in Pregnancy

UIBC changes in conjunction with TIBC. Please read the TIBC article. 

High UIBC in Pregnancy

UIBC 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 UIBC 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 UIBC in Pregnancy

A low UIBC 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 UIBC 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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