Supplement evidence

004 / 575Mineral

Iron

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The short answer

Treating confirmed iron deficiency and iron-deficiency anemia.

Evidence and scope: Established for an indicated use
This status does not grade the ingredient for every goal, outcome, or person.
Important limitation: Fatigue without iron deficiency is not a reason to take iron, and excess does not improve longevity.
Before deciding: Overdose is dangerous; constipation and drug interactions are common. Test before long-term use.

01 / PRACTICAL GUIDE

Dose, absorption, and combinations

These are indication-specific reference or studied ranges—not a personalized prescription. Start with the objective, then check the form, label, medicines, and health conditions.

Reference range by objective

Confirmed deficiencyElemental dose is lab- and formulation-specific; many regimens use 40–65 mg once daily or every other day

Reference or studied range—not a personalized prescription. The product label or a clinician may specify a different dose.

Dose source ↗

More is not automatically better. A clinician or product label may specify a different amount.

Absorption / solubilityFormulation-dependent

Not usefully classified as a fat- or water-soluble vitamin; absorption depends on the salt, extract, delivery system, and meal.

How it is commonly taken

Vitamin C or an empty stomach can increase absorption, but food may improve tolerance.

Do not combine casually

Separate from thyroid medicine, calcium, antacids, and some antibiotics; do not take without evidence of need.

Dose and use source ↗

Dose and use links lead to primary or official source material. Search links are discovery tools, not proof that every returned paper applies.

02 / EVIDENCE

What the research says

We keep supportive, mixed, negative, safety, and contextual findings together. The headline never replaces the underlying papers.

4research papers in this ledger

25unique primary studies represented

1,764unique participants represented

These are audited counts for this JIVANA collection, not search-result totals. Participants are counted once when multiple papers use the same cohort; review papers are not added again to participant totals.

Open the research timelineResearch timeline

Entries are ordered by publication year. A study period appears only when the source reports it.

2024

Mixed or qualifiedPMID 37979057

Daily versus alternate day oral iron therapy in iron deficiency anemia

Hemoglobin and iron indices did not differ clearly; alternate-day dosing produced fewer adverse effects such as nausea, metallic taste, and altered bowel habits.

Published: 2024n=594 participants7 primary studies represented

Study design and methods

Design: Systematic review of randomized and quasi-experimental studies
Population: 594 people with iron-deficiency anemia across 7 studies
Intervention: Daily versus alternate-day oral iron
Outcome: Hemoglobin, iron indices, and adverse effects

Open research record ↗

2023

Mixed or qualifiedPMID 38021373 · NCT05105438

Alternate day versus consecutive day oral iron supplementation in iron-depleted women

At equal total doses, alternate-day dosing did not raise ferritin more, but caused fewer gastrointestinal effects and less iron deficiency at six months.

Published: 2023Duration: 180 days

Study design and methods

Design: Double-masked randomized placebo-controlled trial
Population: 150 young Swiss women with ferritin at or below 30 μg/L
Intervention: 100 mg iron daily for 90 days versus the same total dose on alternate days over 180 days
Outcome: Ferritin, gastrointestinal effects, hepcidin, and persistent deficiency

Study period: 2021–2022

Funding or conflict note: Funded by the Swiss National Science Foundation; authors reported no competing interests.

Open research record ↗

2018

Mixed or qualifiedPMID 29626044

Efficacy of iron supplementation on fatigue and physical capacity in non-anaemic iron-deficient adults

Iron modestly reduced self-reported fatigue, but did not improve objective physical capacity, including maximal oxygen consumption.

Published: 2018n=1,170 participants18 primary studies represented

Study design and methods

Design: Systematic review and meta-analysis of randomized trials
Population: 1,170 iron-deficient but non-anemic adults across 18 unique trials
Intervention: Oral, intramuscular, or intravenous iron versus placebo or active therapy
Outcome: Self-reported fatigue and objective physical capacity

Funding or conflict note: The review reported no competing interests.

Open research record ↗

2015

Safety signalPMID 25700159

Ferrous sulfate supplementation causes significant gastrointestinal side-effects in adults

Ferrous sulfate increased gastrointestinal effects versus placebo and intravenous iron. This overlapping safety review is excluded from the evidence totals.

Published: 2015

Study design and methods

Design: Systematic review and meta-analysis of 43 randomized trials
Population: 6,831 adults receiving ferrous sulfate, placebo, or intravenous iron
Intervention: Oral ferrous sulfate versus placebo or intravenous iron
Outcome: Gastrointestinal adverse effects

Funding or conflict note: Two authors disclosed consulting and a patent related to an iron-supplement material.

Open research record ↗

Unscreened discovery appendix—not evidence1,758 candidate publicationsSearch run: Aug 21, 2026

Complete for the displayed PubMed query at the search timestamp—not for all databases or every possible synonym. Candidates can be irrelevant, duplicate the same study, or report negative findings. They are never summed as evidence or participants until screened.

03 / SOURCES

Start with the source material

Official evidence overviewNIH Office of Dietary Supplements Live PubMed discovery searchNational Library of Medicine

The live search is for discovery only. Search-result counts change and are not included in the audited totals above.

Recent PubMed discovery recordsDirect links to the first 12 records returned by the reproducible search. These are discovery candidates—not reviewed summaries or a count of supportive findings.

04 / EXPERT CONTEXT

Expert context—not evidence

Expert positions are dated context—not scientific evidence. They never raise the evidence status or become consensus by repetition.

No direct, source-verified endorsement is currently recorded. Research authorship or discussion alone is not treated as endorsement.