Ferrous Sulfate
Ferrous Sulfate is a tier 2 form of Iron, used in 160 on-market products and providing 20.1% elemental iron by weight.
160
on-market products
tier 2
quality tier
20.1%
elemental fraction
Basis: FeSO4 x 7H2O, heptahydrate (classic commercial/OTC form; a dried monohydrate at 0.329 also exists -- check specific labels)
Why this tier: Reference-standard iron salt used as the comparator in most bioavailability literature; showed lower apparent bioavailability (26.7%) than bisglycinate chelate (90.9%) in one head-to-head pediatric trial.
Source: Pineda O, Ashmead HD. 2001, PMID 11377130