Iron is an essential nutrient that is vital for blood flow. Lack of iron in the blood causes drowsiness and nausea. Iron has also been used to ease fatigue and to support pregnant women. It can be taken as a pill or liquid extract. Iron can also be injected by a healthcare provider.
100 to 300 milligrams daily
What Research Shows
May Be Effective
Not Enough Data to Assess
Editorial process and description of evidence categories can be found at EBSCO NAT Editorial Process.
It is likely safe to take iron in small doses for a short time. Even short term use can cause constipation, diarrhea, nausea, and vomiting. Large doses may be toxic and should not be taken unless under doctor care for low iron. Women who are pregnant or breastfeeding and children should be especially careful with iron unless under medical supervision. Not enough studies have been done to say whether it is safe to use for a long period. Large doses taken for a long period of time may not be safe.M1, M2
Talk to your doctor about any supplements or therapy you would like to use. Some can interfere with treatment or make conditions worse such as:
A1. Smith GA, Fisher SA, et al. Oral or parenteral iron supplementation to reduce deferral, iron deficiency and/or anaemia in blood donors. Cochrane Database Syst Rec. 2014;(7):CD009532.
A2. Tay HS, Soiza RL. Systematic review and meta-analysis: what is the evidence for oral iron supplementation in treating anaemia in elderly people? Drugs Aging. 2015 Feb;32(2):149-158.
A3. Ng O, Keeler BD, et al. Iron therapy for pre-operative anaemia. Cochrane Database Syst Rev. 2015 Dec 22;(12):CD011588.
A4. Bonovas S, Fiorino G, et al. Intravenous Versus Oral Iron for the Treatment of Anemia in Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Medicine (Baltimore). 2016 Jan;95(2):e2308.
A5. Low MS, Speedy J, et al. Daily iron supplementation for improving anaemia, iron status and health in menstruating women. Cochrane Database Syst Rev. 2016 Apr 18;4:CD009747.
A6. Fernández-Gaxiola AC, De-Regil LM. Intermittent iron supplementation for reducing anaemia and its associated impairments in adolescent and adult menstruating women. Cochrane Database Syst Rev. 2019;1:CD009218.
A7. Fernández-Gaxiola AC, De-Regil LM, et al. Intermittent iron supplementation for reducing anaemia and its associated impairments in adolescent and adult menstruating women. Cochrane Database Syst Rev. 2019;1:CD009218.
B. Cancer Treatment Support
B1. Mhaskar R, Wao H, et al. The role of iron in the management of chemotherapy-induced anemia in cancer patients receiving erythropoiesis-stimulating agents. Cochrane Database Syst Rev. 2016 Feb 4;2:CD009624.
C. Cardiovascular Disease
C1. Fang X, An P, et al. Dietary intake of heme iron and risk of cardiovascular disease: a dose-dependent meta-analysis of prospective cohort studies. Nutr Meta Cardiovasc Dis. 2015;25(1):24-35.
D. Cognitive Function in Breastfed Infants
D1. Cai C, Granger M, et al. Effect of Daily Iron Supplementation in Healthy Exclusively Breastfed Infants: A Systematic Review with Meta-Analysis. Breastfeed Med. 2017 Dec;12(10):597-603.
E1. Houston BL, Hurrie D, et al. Efficacy of iron supplementation on fatigue and physical capacity in non-anemic iron-deficient adults: a systematic review of randomised controlled trials. BMJ Open. 2018;8(4):e019240.
F. Gestational Diabetes Risk
F1. Khambalia AZ, Aimone A, et al. High maternal iron status, dietary iron intake and iron supplement use in pregnancy and risk of gestational diabetes mellitus: a prospective study and systematic review. Diabet Med. 2016 Sep;33(9):1211-1221.
G. Heart Failure
G1. Avni T, Leibovici L, et al. Iron supplementation for the treatment of chronic heart failure and iron deficiency: systematic review and meta-analysis. Eur J Heart Fail. 2012 Apr;14(4):423-429.
G2. Qian C, Wei B, et al. The Efficacy and Safety of Iron Supplementation in Patients With Heart Failure and Iron Deficiency: A Systematic Review and Meta-analysis. Can J Cardiol. 2016 Feb;32(2):151-159.
H. Hip Fracture
H1. Avenell A, Smith TO, et al. Nutritional supplementation for hip fracture aftercare in older people. Cochrane Database Syst Rev. 2016 Nov 30;11:CD001880.
I. Physical Performance
I1. Pasricha SR, Low M, et al. Iron supplementation benefits physical performance in women of reproductive age: a systematic review and meta-analysis. J Nutr. 2014 Jun;144(6):906-914.
J. Pregnancy Support
J1. Peña-Rosas JP, De-Regil LM, et al. Intermittent oral iron supplementation during pregnancy. Cochrane Database Syst Rev. 2015 Oct 19;(10):CD009997.
J2. Peña-Rosas JP, De-Regil LM, et al. Daily oral iron supplementation during pregnancy. Cochrane Database Syst Rev. 2015;(7):CD004736.
J3. Keats EC, Haider BA, et al. Multiple-micronutrient supplementation for women during pregnancy. Cochrane Database Syst Rev. 2019 Mar 14;3:CD004905.
K. Preterm and Low Birthweight Infants
K1. Mills RJ, Davies MW. Enteral iron supplementation in preterm and low birth weight infants. Cochrane Database Syst Rev. 2012 Mar 14;(3):CD005095.
L. Restless Leg Syndrome
L1. Trotti LM, Becker LA. Iron for the treatment of restless leg syndrome. Cochrane Database Syst Rev. 2019;1:CD007834.
M1. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. The National Academies of Sciences, Engineering, Medicine website. Available at: www.nap.edu/books/0309072794/html. Published 2002. Accessed September 9, 2019.
M2. Tolkien Z, Stecher L, et al. Ferrous sulfate supplementation causes significant gastrointestinal side-effects in adults: a systematic review and meta-analysis. PLoS One. 2015 Feb 20;10(2):e0117383.
N1. Balogun OO, da Silva Lopes K, et al. Vitamin supplementation for preventing miscarriage. Cochrane Database Syst Rev. 2016 May 6;(5):CD004073.
Last reviewed February 2020 by EBSCO NAT Review Board Eric Hurwitz, DC
Last Updated: 5/27/2020
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