Iron
Essential mineral for oxygen transport. FDA RDI for adults 4+ is 18 mg per day. Mandatory declaration per 21 CFR 101.36(b)(2).
FDA Reference Data
About Iron
Iron is one of four mandatory dietary ingredients per FDA 21 CFR 101.36(b)(2)(i), alongside vitamin D, calcium, and potassium. FDA RDI is 18 mg/day for adults 4+. Elemental iron must be declared (not the salt weight). Common forms include Ferrous Bisglycinate (~20% elemental Fe), Ferrous Fumarate (~33%), Ferrous Sulfate (~20%), and Ferrous Gluconate (~12%).
Common Supplement Forms
Note: When a salt form is used, the Supplement Facts panel must declare the elemental amount (e.g., “Magnesium 141 mg 34%”), not the salt weight. The salt name appears in the ingredient list below the panel. See %DV calculator for calculation details.
Frequently Asked Questions
Why is iron mandatory on Supplement Facts labels?
FDA 21 CFR 101.36(b)(2)(i) designates iron as one of four mandatory dietary ingredients (with vitamin D, calcium, and potassium) due to its public health significance. Iron deficiency is the most common nutritional deficiency in the United States. If a supplement contains any amount of iron, it must be declared with amount and %DV. If absent, the label must still show "Iron 0 mg 0%".
What is the FDA RDI for iron?
The FDA RDI for iron is 18 mg per day for adults and children 4 years and older (21 CFR 101.9(c)(8)(iv)). This value reflects the higher need for premenopausal women. %DV is calculated as: (declared elemental iron / 18) × 100, rounded to the nearest whole percent.
How do I calculate elemental iron from ferrous salts?
Multiply the salt weight by the elemental percentage. For example, 50 mg of Ferrous Bisglycinate (~20% elemental Fe) yields 10 mg elemental iron. The Supplement Facts panel should declare "Iron 10 mg 56%" (10 mg / 18 mg RDI = 55.6%, rounded to 56%). The salt name (e.g., "Ferrous Bisglycinate") appears in the ingredient list, not the nutrient declaration.
Are there special FDA labeling requirements for iron supplements?
Yes. FDA requires warning labels on iron-containing supplements (21 CFR 101.17(e)) regarding accidental overdose in children under 6. Products with 30 mg or more of elemental iron per dosage unit must include specific warning language about keeping out of reach of children and the dangers of iron overdose.
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