What is the Transferrin Saturation (TSAT) Calculator?

The Transferrin Saturation (TSAT) Calculator computes transferrin saturation percentage, Total Iron-Binding Capacity (TIBC), and Unsaturated Iron-Binding Capacity (UIBC) from standard serum iron and transferrin laboratory values. TSAT represents the percentage of circulating transferrin iron-binding sites currently occupied by iron atoms.

For a comprehensive hematological workup, pair this tool with our Iron Deficiency Calculator and Plasma Volume Calculator.

Mathematical Formulas for Iron Indices

The fundamental relationships governing transferrin and iron binding are:

TSAT (%) = (Serum Iron ÷ TIBC) × 100

TIBC (µg/dL) = Serum Transferrin (mg/dL) × 1.25

UIBC (µg/dL) = TIBC − Serum Iron

Unit Conversion: 1 µmol/L of Iron = 5.585 µg/dL

Clinical Interpretation of TSAT Values

TSAT Level	Clinical State	Associated Conditions
< 20%	Iron Deficiency / Depleted Stores	Iron deficiency anemia, chronic blood loss, poor GI absorption, chronic kidney disease (CKD), heart failure iron deficiency.
20% to 50%	Normal Range	Adequate balance between iron availability and erythropoietic demand.
> 50%	Iron Overload / High Saturation	Hereditary hemochromatosis, repeated blood transfusions, excessive parenteral/oral iron supplementation, acute iron poisoning.

Frequently Asked Questions

What is the difference between TSAT and Ferritin?

Serum ferritin reflects total body iron storage in the liver and reticuloendothelial system, whereas transferrin saturation (TSAT) reflects the immediate availability of iron in circulation for red blood cell production (erythropoiesis). Ferritin is also an acute phase reactant that rises during systemic inflammation, making TSAT a crucial independent marker.

Why is TSAT important in Chronic Kidney Disease (CKD) and Heart Failure?

In patients with CKD or heart failure, functional iron deficiency frequently occurs even with normal or elevated ferritin levels due to hepcidin-mediated iron trapping. Clinical guidelines (such as KDIGO) recommend IV iron therapy when TSAT is ≤ 20% or ≤ 30% with ferritin ≤ 500 ng/mL to optimize response to erythropoiesis-stimulating agents (ESAs) and relieve symptoms.

How does fasting affect serum iron and TSAT?

Serum iron exhibits diurnal variation, peaking in the morning and declining in the evening, and levels surge following recent dietary intake or oral iron pills. Fasting morning blood samples provide the most reproducible and accurate TSAT measurements.

What is UIBC?

Unsaturated Iron-Binding Capacity (UIBC) is the reserve capacity of transferrin that is not yet bound to iron. It is mathematically calculated as Total Iron-Binding Capacity (TIBC) minus Serum Iron.

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Transferrin Saturation Calculator