What is the Unsaturated Iron Binding Capacity test?

The Unsaturated Iron Binding Capacity (UIBC) test measures the portion of transferrin—the main iron transport protein in blood—that is not currently bound to iron. It reflects the reserve capacity of the blood to carry additional iron.

UIBC is typically interpreted alongside serum iron and Total Iron Binding Capacity (TIBC) to give a complete picture of iron metabolism. When iron levels are low, UIBC is usually high, indicating more unused binding sites. When iron levels are high, UIBC is lower.

This test is a key component of iron studies used to investigate iron deficiency, overload, and disorders of iron utilisation.

Why do I need a UIBC test?

Iron imbalance can cause a wide range of symptoms and may not be fully understood with iron levels alone. UIBC helps clarify whether low or high iron is due to absorption, storage, or transport issues.

You may benefit from this test if you experience:

• Persistent fatigue or low energy
• Weakness or reduced exercise tolerance
• Shortness of breath
• Pale skin
• Hair thinning or hair loss
• Known or suspected iron deficiency
• Abnormal iron or ferritin results
• Monitoring response to iron supplementation

UIBC helps distinguish between true iron deficiency and other causes of abnormal iron results.

Benefits of the test

1. Improves iron deficiency assessment
   Identifies unused iron-binding capacity.
2. Complements iron and TIBC tests
   Provides a fuller picture of iron metabolism.
3. Helps explain fatigue and anaemia
   Supports investigation of low iron availability.
4. Useful in chronic illness assessment
   Helps differentiate iron deficiency from inflammation-related changes.
5. Supports monitoring of iron therapy
   Tracks changes during supplementation.
6. Simple blood-based testing
   Requires only one blood sample.
7. Widely used in clinical practice
   Standard component of iron studies.
8. Reduces diagnostic uncertainty
   Helps interpret borderline or conflicting iron results.

Step-by-step: How we offer testing

Clinic-based testing (UK-wide)

• Choose your nearest UK clinic
• Attend your appointment
• A clinician draws a blood sample
• Sample is sent to the laboratory
• Results are issued once analysis is complete

Home or hotel visit (+£60, UK-wide)

• Book a mobile phlebotomist
• Blood sample taken at your home or hotel
• No need to attend a clinic
• Sample securely transported to the laboratory

Your results explained

High UIBC

• Increased unused iron-binding capacity
• UK standard (typical): >45 µmol/L
• Commonly seen in iron deficiency

Normal UIBC

• Balanced iron-binding capacity
• UK standard (typical): 20–45 µmol/L
• Suggests normal iron transport capacity

Low UIBC

• Reduced available binding sites
• UK standard (typical): <20 µmol/L
• May be seen in iron overload, chronic inflammation, or liver disease

UIBC should always be interpreted with serum iron, ferritin, and TIBC.