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Oral Iron Dosing: Absorption Trials and Anemia Context

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In a 2017 trial of 40 iron-depleted women, 60 mg of elemental iron on alternate days produced greater fractional...

In a 2017 trial of 40 iron-depleted women, 60 mg of elemental iron on alternate days produced greater fractional absorption than the same number of doses on consecutive days (21.8% versus 16.3%). A separate 20-woman study found no absorption advantage for split daily dosing. These studies did not establish equivalent hemoglobin recovery or a 36% reduction in gastrointestinal effects.

Key Findings

  • Study 1 enrolled 40 women aged 18-40 with ferritin at or below 25 micrograms/L. Both groups received 14 doses of 60 mg elemental iron, over 14 or 28 days.
  • Fractional absorption was 21.8% with alternate-day dosing and 16.3% with consecutive-day dosing; total absorption was 175.3 mg and 131.0 mg, respectively.
  • Hepcidin was higher during consecutive-day dosing, which helps explain reduced absorption from later doses.
  • Study 2 enrolled 20 women and compared 120 mg once daily with 60 mg twice daily. Absorption did not differ significantly, while split dosing raised hepcidin more.
  • The authors called for confirmation in patients with iron-deficiency anemia. Absorption results should not be presented as demonstrated long-term hemoglobin equivalence or a universal treatment schedule.

Study Details

Iron absorption from oral iron supplements given on consecutive versus alternate days and as single morning doses versus twice-daily split dosing in iron-depleted women: two open-label, randomised controlled trials
Stoffel NU, Cercamondi CI, Brittenham G, Zeder C, Geurts-Moespot AJ, Swinkels DW, et al. — Lancet Haematol (2017)
Two open-label randomized absorption studies enrolled 40 and 20 iron-depleted women. Alternate-day dosing improved fractional absorption; splitting a daily dose did not.
60 participantsModerate

Practical Takeaway

Alternate-day single dosing can improve iron absorption in the studied population and may be useful when choosing an oral-iron regimen. Confirm the cause of iron deficiency and individualize dose, formulation and monitoring with the treating clinician. These absorption trials did not compare iron bisglycinate with sulfate or test mandatory vitamin C co-supplementation.

Summary

Two randomized absorption studies in iron-depleted women compared consecutive-day with alternate-day ferrous sulfate and single with split daily doses. Their endpoints were absorption and hepcidin, not anemia cure.

Related Supplements

Iron

Related Conditions

Immune FunctionChronic Fatigue Syndrome

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Frequently Asked Questions

Should I take iron every day or every other day?

Alternate-day dosing improved absorption in iron-depleted women in the cited trial. The best anemia-treatment schedule also depends on severity, tolerance, response and the reason for deficiency; the trial did not establish a universal schedule.

Did alternate-day dosing reduce side effects by 36%?

That estimate is not established by these cited absorption studies. Their main outcomes were iron absorption and hepcidin, and no grade 3 or 4 adverse events were reported.

Did the study show that bisglycinate is better than sulfate?

No. It used labeled ferrous sulfate to measure absorption and did not compare these formulations.

Do these trials prove faster correction of anemia?

No. They studied iron-depleted women and absorption endpoints. The authors specifically called for confirmation in iron-deficiency anemia; hemoglobin and iron-store recovery require follow-up.

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Supplement Guide

Iron

Use iron for an assessed deficiency or clinician-directed need. Elemental dose, tolerance and follow-up matter; no oral form or dosing schedule suits everyone.

Condition Guide

Immune Function

References

  1. Stoffel NU, Cercamondi CI, Brittenham G, et al. (2017). Iron absorption from oral iron supplements given on consecutive versus alternate days and as single morning doses versus twice-daily split dosing in iron-depleted women: two open-label, randomised controlled trials. The Lancet Haematology. DOI PubMed
  2. Camaschella C (2015). Iron-Deficiency Anemia. New England Journal of Medicine. DOI PubMed