The amount of iron absorbed by the body per unit dosage from a particular iron source depends on several factors — particle size, surface area, ionic charge, and iron content. The first three of these factors contribute to the relative biological value (RBV) of the iron source — a measure of how quickly the iron enters the bloodstream. The iron content is a function of molecular structure, e.g., elemental iron versus ferrous salts like ferrous sulfate (FeSO4), and is a measure of the iron percentage in a unit dose. Multiplying the RBV by the iron content produces the iron absorption per unit dosage.
The small particle size of Reolin iron contributes to higher RBV leading to high absorption per unit dose and higher iron content.