While both forms of iron are available from Feosol in high potency doses, these two irons are absorbed differently by the body:
Carbonyl iron is 100% elemental iron and is gentler on the system than iron salts, such as ferrous sulfate. The absorption is regulated naturally by the body, so it may be prolonged. Each carbonyl iron caplet contains 45 mg of elemental iron, which is the iron available for absorption.
Ferrous sulfate is an iron salt, and it is 20% elemental iron. For many years, ferrous sulfate has been the type of iron most familiar to doctors, making it the most commonly recommended. Each ferrous sulfate tablet contains 65 mg of elemental iron, which is the iron available for absorption.