Iron

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    Wyatt Brown, Giulia Guerrini

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    by:

    Nick Milazzo
    Last Updated: December 18, 2023

    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.

    153 references on this page
    78,307 participants in 9 trials and 14 meta-analyses

    Overview

    Dosage information

    The recommended daily allowance (RDA) depends on gender, age, and whether you are pregnant or lactating:[1][2]

    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

    These values correspond to the RDA for total iron, which encompasses both dietary iron (iron assimilated from iron-rich foods) and iron supplements. The need for supplementation depends on the amount of iron absorbed from one's diet. It’s important to avoid exceeding the RDA to prevent excessive iron intake.[1]

    Notably, for infants up to 6 months of age, these values specifically refer to adequate intake (AI), because there is insufficient evidence to establish an RDA for this age group.[1] The Institute of Medicine (IOM) determined the daily AI by multiplying the average iron content in human milk (0.35 mg/L) by the average milk intake of exclusively breastfed infants (0.78 L/day), resulting in an AI of 0.27 mg/day of iron. These values don’t account for potential variations in the iron concentration of human milk.[3]

    For preterm breastfed infants, a daily oral iron dosage of approximately 2 mg/kg is estimated to be appropriate for preventing iron deficiency (ID) or iron deficiency anemia (IDA) in preterm breastfed babies. Term breastfed infants typically do not require additional iron until around 4 months, at which point supplementation with 1 mg/kg of iron may or may not be required depending on the infant's health status. Formula-fed preterm and term infants may require different dosages if iron supplementation is needed.[2]

    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.[4]

    Examine Database: Iron

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    Examine Database References

    1. Depression Symptoms - McClung JP, Karl JP, Cable SJ, Williams KW, Nindl BC, Young AJ, Lieberman HRRandomized, double-blind, placebo-controlled trial of iron supplementation in female soldiers during military training: effects on iron status, physical performance, and moodAm J Clin Nutr.(2009 Jul)
    2. Aerobic Exercise Metrics - Waldvogel S, Pedrazzini B, Vaucher P, Bize R, Cornuz J, Tissot JD, Favrat BClinical evaluation of iron treatment efficiency among non-anemic but iron-deficient female blood donors: a randomized controlled trialBMC Med.(2012 Jan 24)
    3. Stress Signs and Symptoms - Favrat B, Balck K, Breymann C, Hedenus M, Keller T, Mezzacasa A, Gasche CEvaluation of a single dose of ferric carboxymaltose in fatigued, iron-deficient women--PREFER a randomized, placebo-controlled studyPLoS One.(2014 Apr 21)
    4. Hemoglobin - Ali SA, Razzaq S, Aziz S, Allana A, Ali AA, Naeem S, Khowaja N, Ur Rehman FRole of iron in the reduction of anemia among women of reproductive age in low-middle income countries: insights from systematic review and meta-analysis.BMC Womens Health.(2023-Apr-17)
    5. Hemoglobin - Andersen CT, Marsden DM, Duggan CP, Liu E, Mozaffarian D, Fawzi WWOral iron supplementation and anaemia in children according to schedule, duration, dose and cosupplementation: a systematic review and meta-analysis of 129 randomised trials.BMJ Glob Health.(2023-Feb)
    6. Hemoglobin - Banerjee A, Athalye S, Shingade P, Khargekar V, Mahajan N, Madkaikar M, Khargekar NEfficacy of daily versus intermittent oral iron supplementation for prevention of anaemia among pregnant women: a systematic review and meta-analysis.EClinicalMedicine.(2024 Jul 17)
    7. Heart Rate - Brownlie T 4th, Utermohlen V, Hinton PS, Giordano C, Haas JDMarginal iron deficiency without anemia impairs aerobic adaptation among previously untrained womenAm J Clin Nutr.(2002 Apr)
    8. Muscular Endurance - Brutsaert TD, Hernandez-Cordero S, Rivera J, Viola T, Hughes G, Haas JDIron supplementation improves progressive fatigue resistance during dynamic knee extensor exercise in iron-depleted, nonanemic womenAm J Clin Nutr.(2003 Feb)
    9. Anxiety Symptoms - Vaucher P, Druais PL, Waldvogel S, Favrat BEffect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin: a randomized controlled trialCMAJ.(2012 Aug 7)
    10. Exercise Capacity - Houston BL, Hurrie D, Graham J, Perija B, Rimmer E, Rabbani R, Bernstein CN, Turgeon AF, Fergusson DA, Houston DS, Abou-Setta AM, Zarychanski REfficacy of iron supplementation on fatigue and physical capacity in non-anaemic iron-deficient adults: a systematic review of randomised controlled trialsBMJ Open.(2018 Apr 5)
    11. Aerobic Exercise Metrics - Woods A, Garvican-Lewis LA, Saunders PU, Lovell G, Hughes D, Fazakerley R, Anderson B, Gore CJ, Thompson KGFour weeks of IV iron supplementation reduces perceived fatigue and mood disturbance in distance runnersPLoS One.(2014 Sep 23)
    12. Fibromyalgia Symptoms - Chad S Boomershine, Todd A Koch, David MorrisA Blinded, Randomized, Placebo-Controlled Study to Investigate the Efficacy and Safety of Ferric Carboxymaltose in Iron-Deficient Patients with FibromyalgiaRheumatol Ther.(2018 Jun)
    13. Hemoglobin - Fischer JAJ, Cherian AM, Bone JN, Karakochuk CDThe effects of oral ferrous bisglycinate supplementation on hemoglobin and ferritin concentrations in adults and children: a systematic review and meta-analysis of randomized controlled trials.Nutr Rev.(2023-Jul-10)
    14. Hemoglobin - Silva Neto LGR, Santos Neto JED, Bueno NB, de Oliveira SL, Ataide TDREffects of iron supplementation versus dietary iron on the nutritional iron status: Systematic review with meta-analysis of randomized controlled trials.Crit Rev Food Sci Nutr.(2019)
    15. Hemoglobin - Fernández-Gaxiola AC, De-Regil LMIntermittent iron supplementation for reducing anaemia and its associated impairments in adolescent and adult menstruating womenCochrane Database Syst Rev.(2019 Jan 31)
    16. Hemoglobin - Watt A, Eaton H, Eastwick-Jones K, Thomas ET, Plüddemann AThe benefits and harms of oral iron supplementation in non-anaemic pregnant women: a systematic review and meta-analysis.Fam Pract.(2025 Jan 21)
    17. Infant Birth Weight - Hansen R, Sejer EPF, Holm C, Schroll JBIron supplements in pregnant women with normal iron status: A systematic review and meta-analysis.Acta Obstet Gynecol Scand.(2023-Sep)
    18. Attention - Gutema BT, Sorrie MB, Megersa ND, Yesera GE, Yeshitila YG, Pauwels NS, De Henauw S, Abbeddou SEffects of iron supplementation on cognitive development in school-age children: Systematic review and meta-analysis.PLoS One.(2023)
    19. Attention - Chen Z, Yang H, Wang D, Sudfeld CR, Zhao A, Xin Y, Chen JC, Fawzi WW, Xing Y, Li ZEffect of Oral Iron Supplementation on Cognitive Function among Children and Adolescents in Low- and Middle-Income Countries: A Systematic Review and Meta-Analysis.Nutrients.(2022-Dec-15)
    20. All-Cause Mortality - Mei Z, Chen J, Luo S, Jin L, Liu Q, Chen YComparative efficacy of intravenous and oral iron supplements for the treatment of iron deficiency in patients with heart failure: A network meta-analysis of randomized controlled trials.Pharmacol Res.(2022-Aug)
    21. Cardiovascular Mortality - Hamed M, Elseidy SA, Ahmed A, Thakker R, Mansoor H, Khalili H, Mohsen A, Mamas MA, Banerjee S, Kumbhani DJ, Elgendy IY, Elbadawi AIntravenous iron therapy among patients with heart failure and iron deficiency: An updated meta-analysis of randomized controlled trials.Heliyon.(2023-Jun)