“Iron supplements improve fatigue in people who are not iron-deficient.”
Iron supplements have not been shown to ease tiredness in people whose iron stores are normal.
If your iron stores are normal, extra iron is unlikely to help your tiredness. Because a normal blood count can miss low iron stores, a test answers the question better than trying a supplement.
Before taking iron for tiredness, ask for a ferritin test along with a blood count.
Safety note: Iron supplements are dangerous for young children: by federal label rule, iron products must warn that accidental overdose is a leading cause of fatal poisoning in children under 6, so store them out of reach. People with hemochromatosis, a condition that causes iron overload, are advised to avoid supplements that contain iron or vitamin C, which increases iron absorption.
Talk to a healthcare professional if: you have been tired for weeks without a clear reason, you are thinking of taking iron every day for more than a few weeks, or you have hemochromatosis.
The trials that found less tiredness enrolled women with low or borderline iron stores, and in one trial only women with ferritin at or below 50 micrograms per liter improved. We found no trial showing a benefit when iron stores are normal, but few trials have tested that group directly, so confidence is limited.
Iron supplements have not been shown to ease tiredness in people whose iron stores are normal. The benefit seen in trials was in women with low or borderline iron stores, even though their blood counts did not show anemia.
In a 2003 Swiss trial, 144 women aged 18 to 55 with unexplained tiredness and no anemia took 80 mg of iron a day or a placebo for four weeks. Tiredness fell 29 percent with iron and 13 percent with placebo, but only women with ferritin (a blood marker of iron stores) at or below 50 micrograms per liter improved; about half had ferritin at or below 20. A 2012 French trial enrolled only women aged 18 to 53 with ferritin below 50 and no anemia; after 12 weeks, fatigue scores fell 47.7 percent with iron and 28.8 percent with placebo, with no change in quality of life, depression or anxiety. A 2018 review of 18 trials in 1,170 adults who were iron deficient but not anemic found less self-reported tiredness with iron but no improvement in measured physical fitness. A normal blood count does not always mean normal iron stores.
- Verdon F, Burnand B, Stubi CL, et al. Iron supplementation for unexplained fatigue in non-anaemic women: double blind randomised placebo controlled trial. BMJ. 2003;326(7399):1124. DOI: 10.1136/bmj.326.7399.1124. PMID: 12763985. PMCID: PMC156009
- Vaucher P, Druais PL, Waldvogel S, Favrat B. Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin: a randomized controlled trial. CMAJ. 2012;184(11):1247-1254. DOI: 10.1503/cmaj.110950. PMID: 22777991. PMCID: PMC3414597
- Houston BL, Hurrie D, Graham J, et al. Efficacy of iron supplementation on fatigue and physical capacity in non-anaemic iron-deficient adults: a systematic review of randomised controlled trials. BMJ Open. 2018;8(4):e019240. DOI: 10.1136/bmjopen-2017-019240. PMID: 29626044. PMCID: PMC5892776
- U.S. Code of Federal Regulations. 21 CFR 101.17(e): Dietary supplements containing iron or iron salts. Via Cornell Legal Information Institute
- National Institute of Diabetes and Digestive and Kidney Diseases. Eating, Diet, and Nutrition for Hemochromatosis. Last reviewed January 2020