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Iron for tiredness

Goal: What trials of iron used for tiredness in people with low iron stores but no anemia.

Each protocol describes what studies used, for one goal or for one group of people. It is not advice for you: talk to a doctor before you start a supplement.

Updated 9 Nov 2026
Dose

80 mg of elemental iron a day in a trial of 198 tired women with low ferritin.[1] The trials in the 2018 review gave many doses, by mouth, into a muscle or into a vein.[2]

Form

Ferrous sulfate tablets in that trial.[1]

When to take

Every day.[1]

How long

12 weeks.[1]

What studies found

A 2018 review found less self-reported fatigue in 4 trials with 714 adults who had low iron but no anemia (standardized mean difference 0.38). Two of the trials gave iron by mouth and two into a vein. Measured physical capacity did not change.[2] In 198 tired women with ferritin below 50 µg/L, the fatigue score fell by 47.7% with iron and by 28.8% with placebo.[1]

Ask a doctor first

These results apply to people with low iron stores. In a 2025 review, the effects of iron disappeared when people with iron deficiency were left out.[3] In men and in women after menopause, low iron usually comes from blood loss in the gut or poor absorption, and a doctor looks for the source.[4] The US upper limit is 45 mg a day for adults, and doctors sometimes prescribe more to treat iron deficiency anemia.[5]

Ask a doctor before taking iron for tiredness. Ferritin, a blood test of iron stores, is the most efficient test for iron deficiency.[5]

References

  1. Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin: a randomized controlled trial. Vaucher P, Druais PL, Waldvogel S, Favrat B CMAJ, 2012. PMID 22777991
  2. Efficacy of iron supplementation on fatigue and physical capacity in non-anaemic iron-deficient adults: a systematic review of randomised controlled trials. Houston BL, Hurrie D, Graham J, Perija B, Rimmer E, Rabbani R, et al. BMJ Open, 2018. PMID 29626044
  3. Psychiatric and cognitive outcomes of iron supplementation in non-anemic children, adolescents, and menstruating adults: A meta-analysis and systematic review. Fiani D, Chahine S, Zaboube M, Solmi M, Powers JM, Calarge C Neurosci Biobehav Rev, 2025. PMID 40945632
  4. The diagnosis and treatment of iron deficiency and its potential relationship to hair loss. Trost LB, Bergfeld WF, Calogeras E J Am Acad Dermatol, 2006. PMID 16635664
  5. Iron: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov