Transferrin saturation
What it measures, and what changes the number.
Transferrin saturation describes how much of the iron-carrying capacity of transferrin is actually occupied by iron. It is not measured directly but calculated from serum iron and either transferrin or TIBC, and it is expressed as a percentage.
It is read with serum iron, ferritin, transferrin and TIBC as part of an iron panel. Ferritin reflects stored iron, while saturation reflects iron that is currently in circulation, so the two are often looked at together.
Serum iron rises and falls over the day and after meals or iron-containing supplements, and because saturation is calculated from it, the same variation carries through. Many labs prefer a morning, fasting sample for this reason. Labs may report it as % SATURATION or Índice de saturación de transferrina.
Often read alongside: Iron, Transferrin, TIBC, Ferritin