Supplement Label Index

Ferrous/Iron Bisglycinate Chelate vs. Ferrous Sulfate

Among 1,931 on-market iron products with an identifiable primary form, 15.2% use Ferrous/Iron Bisglycinate Chelate (293 products) and 8.2% use Ferrous Sulfate (159).

Ferrous/Iron Bisglycinate ChelateFerrous Sulfate
Quality tierTier 1Tier 2
Iron by weight27.4%20.1%
Share of market15.2%8.2%
On-market products293159
Median declared dose10 elemental mg
middle half: 6–18
18 elemental mg
middle half: 11.5–65
Most common brandsBluebonnet, Solgar, MegaFoodGeri-Care, Rugby, Major

Doses are declared per serving in elemental mg. “By weight” is the share of the ingredient that is the nutrient itself (e.g. elemental magnesium in a magnesium salt).

Why Ferrous/Iron Bisglycinate Chelate is tier 1

Apparent bioavailability 90.9% vs. 26.7% for ferrous sulfate in a pediatric iron-deficiency-anemia RCT; only the chelate group showed a significant ferritin increase.

Source: Pineda O, Ashmead HD. 2001, Nutrition 17(5):381-384, PMID 11377130

Why Ferrous Sulfate is tier 2

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

Tiers summarize published comparative bioavailability or outcome evidence for each form (see methodology). This page describes the market; it is not a recommendation to take either form. Talk to a clinician about what's right for you.

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