Iron

    Written by:
    Wyatt Brown, Giulia Guerrini
    Fact-checked by:
    Nick Milazzo, Gregory Lopez
    Last Updated: March 19, 2026

    Iron is an essential mineral best known for helping red blood cells to carry oxygen. Except in the case of deficiency, iron supplementation has no proven benefit; on the contrary, it can lead to side effects and increased oxidative stress.

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    Overview

    Dosage Information

    Formulation

    Iron is available orally as a tablet, capsule, or liquid in various chemical forms including the following:[1]

    • Iron salts (e.g., ferrous gluconate, ferrous sulfate, ferrous fumarate)
    • Iron-amino acid chelates (e.g., ferrous bisglycinate)
    • Iron-polysaccharide complexes
    • Heme-iron polypeptides
    • Liposomal iron
    • Lipophilic iron chelates (e.g., ferric maltol)

    The amount of elemental iron and its bioavailability can vary depending on the form of iron. For more information, see our FAQ How do different iron forms compare?

    Range of dosages studied

    Iron has been studied at dosages ranging from 1 mg to 300 mg of elemental iron daily, divided one to three times throughout the day. Less frequent dosing has been used, ranging from once weekly to every other day.[2][3]

    Iron RDA

    The recommended dietary allowance (RDA) depends on gender, age, and whether you are pregnant or lactating.[4][5]

    AgeMaleFemalePregnancyLactation
    0–6 months0.27 mg*0.27 mg*
    7–12 months11 mg11 mg
    1–3 years7 mg7 mg
    4–8 years10 mg10 mg
    9–13 years8 mg8 mg
    14–18 years11 mg15 mg27 mg10 mg
    19–50 years8 mg18 mg27 mg9 mg
    51+ years8 mg8 mg

    * Adequate intake (AI)
    Reference: Institute of Medicine. Iron (chapter 9 in Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. The National Academies Press. 2001. DOI:10.17226/10026

    These values correspond to the RDA for total iron, which includes both dietary iron (iron assimilated from iron-rich foods) and iron supplements.[4]

    Notably, for infants up to 6 months of age, these values specifically refer to the adequate intake (AI), because there is insufficient evidence to establish an RDA for this age group. It is based on the average amount of iron obtained through breast milk.[4]

    For preterm infants who are breastfed, a daily oral iron dosage of approximately 2 mg per kg of body weight taken until 12 months of age is estimated to be appropriate for preventing iron deficiency or iron deficiency anemia. Full-term infants who are breastfed typically do not require additional iron until around 4 months, at which point supplementation with 1 mg per kg of body weight of iron may or may not be required depending on the infant's health status and intake of iron-containing foods. Because formula is usually fortified with iron, formula-fed preterm and full-term infants may require different dosages if iron supplementation is needed.[5]

    Iron UL

    The tolerable upper intake level (UL) is the maximum daily amount of iron from supplements that is unlikely to cause gastrointestinal distress.

    AgeMaleFemalePregnancyLactation
    0–12 months40 mg40 mg
    1–13 years40 mg40 mg
    14–50 years45 mg45 mg45 mg45 mg
    51+ years45 mg45 mg

    Reference: Institute of Medicine. Iron (chapter 9 in Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. USA: The National Academies Press. 2001. DOI:10.17226/10026

    Other considerations

    It is worth noting that iron is most effective when administered on an empty stomach or 2 hours after a meal. However, if iron supplements are poorly tolerated due to gastrointestinal side effects, a dose reduction or administration after a meal may be more suitable.[6]

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