Calculating and Interpreting Transferrin Saturation

Calculation and Formula

The Centers for Disease Control and Prevention recommends calculating Transferrin Saturation (TSAT) by dividing serum iron concentration by total iron-binding capacity (TIBC) and multiplying by 100 1, 2
The formula for TSAT is: TSAT (%) = (serum iron / TIBC) × 100 1, 2
Transferrin can be converted to TIBC using the formula: TIBC (μmol/L) = Transferrin (g/L) × 25.1 3, 2

A TSAT of 51.4% indicates that approximately half of the transferrin binding sites are occupied by iron, according to the American Journal of Kidney Diseases 3
The normal TSAT range in adults is typically 20-50%, as stated by Clinical Nutrition 4
Low TSAT (<20%) is often used to confirm iron deficiency, as recommended by the Centers for Disease Control and Prevention 1, 6
High TSAT (>50%) may indicate iron overload conditions, according to the American Journal of Kidney Diseases 3
TSAT is an indicator of iron-deficient erythropoiesis rather than iron depletion, and is less sensitive to changes in iron stores than serum ferritin concentration, as reported by the Centers for Disease Control and Prevention 7, 8

Diurnal variation, recent meals, inflammation, and infection can affect serum iron concentration and TSAT measurement, as noted by the Centers for Disease Control and Prevention 9, 10
Day-to-day variation within individuals is greater for TSAT than for hemoglobin concentration, according to the Centers for Disease Control and Prevention 9, 10
Other conditions such as inflammation, chronic infection, malignancies, liver disease, nephrotic syndrome, malnutrition, oral contraceptive use, and pregnancy can affect TIBC and TSAT measurement, as reported by the Centers for Disease Control and Prevention 9, 10