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Iron Human Clinical Research: What the Evidence Shows

Last updated: October 2026. This article is for educational purposes and is not medical advice.

1. Executive Evidence Summary

Iron is one of the most thoroughly studied nutrients in human research. Hundreds of randomized trials and many systematic reviews have tested oral iron supplements in pregnant women, infants, children, menstruating women, athletes and patients with chronic disease. This page summarizes what those human studies show, how reliable the findings are and where the evidence is weak.

The overall picture is consistent. Oral iron reliably corrects iron deficiency and iron deficiency anemia, with average hemoglobin gains that are statistically clear but modest in absolute terms. In pregnancy, daily iron sharply lowers the risk of maternal anemia at term and probably reduces low birth weight. In people who are iron deficient but not anemic, iron can reduce fatigue. In people who are iron replete, there is no good evidence of benefit, and there are signs of harm in specific settings such as malaria-endemic regions.

Evidence at a Glance

•       Strongest evidence: correction of anemia and iron deficiency in pregnancy, childhood and women of reproductive age.

•       Moderate evidence: reduced fatigue in non-anemic iron deficiency, lower side effects with lower or alternate-day dosing, and fewer gastrointestinal complaints with gentler iron forms such as ferrous bisglycinate.

•       Limited evidence: cognition, athletic performance, restless legs symptoms and outcomes in chronic disease when oral iron is used.

•       No supportive evidence: benefit in iron-replete people.

•       Main safety signals: gastrointestinal effects, accidental overdose in children, iron overload conditions, and infection risk in some high-malaria settings.

2. Research Question

This page asks one broad question and several narrower ones.

Primary question: In humans, does oral iron supplementation improve clinically meaningful health outcomes, and how large and reliable are those effects?

•       Does iron improve hemoglobin and ferritin, and in which populations?

•       Does it improve outcomes that people feel or that matter clinically, such as fatigue, exercise capacity, cognition, birth weight and development?

•       How do doses, schedules and iron forms (ferrous sulfate, ferrous bisglycinate and others) compare for effect and tolerability?

•       What are the safety risks, and who is harmed rather than helped?

The scope is human clinical research on oral iron. Animal studies, cell studies and intravenous iron are mentioned only where they help interpret human findings.

3. Search and Inclusion Methodology

This article is a narrative evidence synthesis, not a new formal systematic review. It was prepared by reviewing major randomized controlled trials, Cochrane reviews, other systematic reviews and meta-analyses, human isotope absorption studies and authoritative guidelines. No new database search protocol was registered or run for this page, so it should not be read as a PRISMA-compliant review.

Inclusion Priorities

•       Randomized controlled trials and systematic reviews of randomized trials.

•       Human studies of oral iron, including specific forms such as ferrous bisglycinate.

•       Studies reporting hematological outcomes (hemoglobin, ferritin) and functional or clinical outcomes (fatigue, birth weight, development, exercise capacity).

•       Safety data from trials and large reviews.

Exclusions

•       Animal and in vitro studies as primary evidence.

•       Uncontrolled case series, except to illustrate gaps.

•       Manufacturer marketing claims without peer-reviewed support.

Evidence Weighting

Systematic reviews and large randomized trials carry the most weight. Small trials, short studies and trials funded by ingredient manufacturers are weighted more cautiously. Readers should verify all citations against the original publications, because details such as effect sizes can differ between versions and updates.

4. Evidence by Health Outcome

Iron Deficiency Anemia and Iron Status

This is the best-supported use. Across populations, oral iron raises hemoglobin and ferritin and lowers the proportion of people with anemia. A Cochrane review of daily iron in menstruating women (Low et al., 2016) found that supplementation reduced anemia by roughly 60% and raised hemoglobin by about 5 g/L (0.5 g/dL) on average, with larger gains in those who started with anemia. Effects in people who are already iron replete are small, as expected.

Pregnancy

The Cochrane review of daily oral iron in pregnancy (Pena-Rosas et al., 2015) found that iron reduced the risk of maternal anemia at term by about 70% and the risk of iron deficiency at term substantially. Low birth weight appeared less common among women who took iron, while the effect on preterm birth was not clear. A separate meta-analysis (Haider et al., 2013) reported lower risks of low birth weight and maternal anemia with prenatal iron. Side effects were more common with iron, and this is why lower doses and better-tolerated forms are of interest. In a randomized trial, 25 mg of iron as ferrous bisglycinate matched 50 mg as ferrous sulfate for preventing deficiency and anemia in pregnancy (Milman et al., 2014).

Infants and Children

A systematic review of children aged 4 to 23 months (Pasricha et al., 2013) found that daily iron increased hemoglobin by close to 1 g/dL and substantially reduced anemia and iron deficiency. Evidence for developmental benefit is less clear. Iron deficiency in early life is linked to poorer cognitive outcomes, but trials of supplementation show smaller and less consistent benefits, and they are limited by timing, duration and baseline status (Larson et al., 2017). Trials of ferrous bisglycinate in children, such as Pineda and Ashmead (2001) and Duque et al. (2014), report improvement in hemoglobin or ferritin, though they do not consistently show superiority over ferrous sulfate.

Fatigue in Non-Anemic Iron Deficiency

A systematic review and meta-analysis of randomized trials in non-anemic iron-deficient adults (Houston et al., 2018) found that iron supplementation reduced fatigue compared with placebo. The effect was moderate, and the trials were small and heterogeneous. The benefit is specific to deficiency. It should not be extrapolated to people with normal ferritin.

Exercise Capacity and Athletes

A systematic review in iron-deficient but non-anemic athletes (Burden et al., 2015) found that iron treatment improved iron status, with some evidence of improved maximal oxygen uptake, although results on performance were inconsistent. Menstruating women in the Cochrane review also showed improvements in physical performance measures. There is no good evidence that iron improves performance in athletes with adequate iron stores.

Restless Legs Syndrome

Iron deficiency is associated with restless legs syndrome, and iron therapy is used in clinical practice. A Cochrane review (Trotti and Becker, 2019) concluded that intravenous iron probably improves symptoms in some patients, while evidence for oral iron was of low quality. Oral iron may still be reasonable in mild deficiency, but the supporting trials are limited.

Heart Failure

Intravenous iron improved symptoms and functional capacity in iron-deficient heart failure patients in trials such as FAIR-HF (Anker et al., 2009). By contrast, the IRONOUT-HF trial (Lewis et al., 2017) found that high-dose oral iron did not improve exercise capacity. This is a clear example of the route of administration changing the answer, and it shows that oral iron results cannot be generalized to every clinical context.

Safety Outcomes

Gastrointestinal side effects are the main tolerability problem. A meta-analysis found that ferrous sulfate significantly increased gastrointestinal adverse events compared with placebo (Tolkien et al., 2015). In malaria-endemic settings, a large trial in Pemba, Tanzania found more serious adverse events with routine iron and folic acid in children who were not iron deficient (Sazawal et al., 2006). A later Cochrane review (Neuberger et al., 2016) concluded that iron does not increase clinical malaria when malaria prevention and treatment are available. Together, these findings support targeted rather than universal supplementation where infection risk is high.

5. Human Studies Table

The table lists key human studies and reviews that anchor the evidence. It is a selection, not an exhaustive list.

Study	Population	Intervention	Main finding
Low et al., 2016 (Cochrane)	Menstruating women	Daily oral iron vs control	Less anemia; hemoglobin gain of about 0.5 g/dL; some improvement in physical performance
Pena-Rosas et al., 2015 (Cochrane)	Pregnant women	Daily oral iron vs control	Much lower anemia and iron deficiency at term; probable reduction in low birth weight
Haider et al., 2013	Pregnant women	Prenatal iron (meta-analysis)	Lower risk of maternal anemia and low birth weight
Pasricha et al., 2013	Children 4–23 months	Daily iron vs control	Higher hemoglobin; less anemia and iron deficiency
Milman et al., 2014	Pregnant women	25 mg iron as bisglycinate vs 50 mg as sulfate	Similar iron status; fewer gastrointestinal complaints with bisglycinate
Pineda and Ashmead, 2001	Infants and young children with anemia	Ferrous bisglycinate	Improved hemoglobin and ferritin; study linked to manufacturer
Duque et al., 2014	Schoolchildren	Ferrous sulfate vs iron bisglycinate	Ferritin improved with both forms
Fischer et al., 2023	Adults and children	Ferrous bisglycinate (meta-analysis)	Higher hemoglobin in pregnancy than other iron forms; fewer GI events; limited evidence elsewhere
Houston et al., 2018	Non-anemic iron-deficient adults	Iron vs placebo	Reduced fatigue
Rimon et al., 2005	Older anemic patients	15, 50 or 150 mg daily	Similar hemoglobin response with fewer side effects at the lowest dose
Stoffel et al., 2017, 2020	Iron-depleted or iron-deficient women	Alternate-day vs consecutive-day dosing (isotope studies)	Higher fractional absorption with alternate-day dosing
Tolkien et al., 2015	Adults	Ferrous sulfate vs placebo	More gastrointestinal side effects with iron
Sazawal et al., 2006	Preschool children, high-malaria setting	Iron and folic acid vs placebo	More serious adverse events in non-deficient children
Lewis et al., 2017 (IRONOUT-HF)	Heart failure	High-dose oral iron vs placebo	No improvement in exercise capacity

 

6. Study Design Quality

Most of the strongest evidence comes from randomized controlled trials and from Cochrane or similar systematic reviews, which is a favorable design profile. Several features limit certainty, however.

•       Blinding problems. Iron causes dark stools and gastrointestinal effects, which can unblind participants, particularly in trials against placebo, and this may affect symptom outcomes such as fatigue.

•       Small trials of specific forms. Many trials of ferrous bisglycinate are small, short or conducted by groups linked to the manufacturer.

•       Variable baseline status. Trials mix deficient and replete participants, which dilutes effects and complicates interpretation.

•       Surrogate endpoints. Most trials measure hemoglobin and ferritin, not symptoms or clinical events.

•       Heterogeneity. Doses, durations, populations and iron forms vary widely.

•       Reporting quality. Side effect reporting is inconsistent, and many older trials give limited methodological detail.

Overall, the design quality is good for hematological outcomes and moderate for symptoms, development and form-to-form comparisons.

7. Participant Characteristics

The evidence base is dominated by specific groups, and this affects how widely the results apply.

•       Pregnant women: well represented, from high-income and low-income countries.

•       Infants and young children: heavily studied in low- and middle-income countries, where anemia prevalence is high.

•       Menstruating women: well studied, often with mild or moderate deficiency.

•       Adolescents and athletes: smaller evidence base.

•       Older adults: limited, with small trials such as Rimon et al. (2005).

•       Men: underrepresented, partly because iron deficiency is less common.

•       Patients with chronic disease: heart failure, kidney disease and inflammatory bowel disease are studied mainly with intravenous iron.

Participants in many trials had confirmed deficiency or anemia, so results apply mainly to people with a demonstrated need. Evidence for healthy, iron-replete adults is sparse because there is no expected benefit.

8. Dose and Form Used

Trials have used a wide range of oral iron doses, usually expressed as elemental iron.

Population	Typical doses in trials	Forms commonly studied
Pregnancy	25 to 60 mg per day; some higher for treatment	Ferrous sulfate, fumarate, bisglycinate
Menstruating women	30 to 120 mg per day	Ferrous sulfate, fumarate, gluconate, bisglycinate
Infants and children	Weight-based, often 1 to 3 mg per kg per day	Ferrous sulfate drops, bisglycinate, fortified foods
Older adults	15 to 150 mg per day	Ferrous sulfate, others
Isotope absorption studies	Often 40 to 120 mg given as single or split doses	Ferrous sulfate

 

Dose comparisons show diminishing returns. Rimon et al. (2005) found similar hemoglobin responses with 15 mg and 150 mg per day in older anemic patients, with fewer side effects at the low dose. Isotope studies explain why: a dose raises hepcidin, which reduces absorption from further doses for up to about 48 hours (Moretti et al., 2015; Stoffel et al., 2017).

Ferrous sulfate is the reference comparator in most trials. Evidence for ferrous bisglycinate is smaller but consistent in direction: matching efficacy at lower doses in pregnancy and fewer gastrointestinal complaints, according to Milman et al. (2014) and the meta-analysis by Fischer et al. (2023). Evidence for other forms such as carbonyl iron, polysaccharide iron and heme iron polypeptide is more limited.

9. Duration

Trial durations range from a few weeks to several months, and the choice affects what can be detected.

•       Short trials (2 to 4 weeks): can detect hemoglobin responses and side effects.

•       Medium trials (8 to 12 weeks): typical for anemia and fatigue studies, and long enough to see ferritin changes.

•       Pregnancy trials: run through the second and third trimesters, often several months.

•       Child development trials: rarely longer than several months, which limits conclusions about long-term outcomes.

Clinical guidance commonly recommends continuing iron for about three months after hemoglobin normalizes to rebuild stores. Evidence for the benefit of long-term, indefinite supplementation in people without ongoing losses is weak, and long-term safety data are limited.

10. Primary Endpoints

Endpoints fall into three tiers, and the strength of evidence differs by tier.

•       Laboratory endpoints: hemoglobin, ferritin, transferrin saturation, serum iron. These are the most common and most consistently improved.

•       Clinical and functional endpoints: fatigue scores, exercise capacity, cognitive tests, developmental scores, birth weight. These are less often measured and show smaller effects.

•       Safety and tolerability endpoints: gastrointestinal symptoms, adherence, infections, serious adverse events.

A recurring weakness is that hemoglobin and ferritin are surrogate markers. Improving them does not automatically improve how patients feel or function, so functional endpoints deserve closer attention.

11. Results

Outcome	Direction	Summary of results
Hemoglobin in anemic people	Improved	Consistent increase; magnitude depends on baseline and dose
Ferritin and iron stores	Improved	Clear increases, often within 8 to 12 weeks
Maternal anemia at term	Improved	About 70% lower risk in Cochrane analysis
Low birth weight	Probably improved	Lower risk in meta-analyses; effect on preterm birth unclear
Child anemia and iron deficiency	Improved	Large reductions in risk
Child cognition and development	Unclear	Small or inconsistent benefits
Fatigue in non-anemic iron deficiency	Improved	Moderate effect in pooled analyses
Athletic performance	Mixed	Possible benefit only if deficient
Restless legs symptoms	Mixed	IV iron more convincing than oral
Heart failure exercise capacity	No benefit with oral iron	IV iron beneficial; oral iron not
Gastrointestinal side effects	Worsened with iron	Common with ferrous sulfate; lower with some forms or regimens
Serious adverse events in high-malaria settings	Possibly worsened	Seen in one large trial; later review found no increased malaria with proper malaria care

 

12. Clinical Significance

Statistical significance and clinical significance are not the same thing.

•       Hemoglobin gains: an average rise of about 0.5 g/dL in menstruating women or close to 1 g/dL in young children is modest, but in an individual with severe anemia the rise can be much larger. Averages hide that heterogeneity.

•       Anemia prevention in pregnancy: a 70% lower risk of anemia at term is a large, clinically important effect, because anemia in pregnancy is linked to maternal and infant complications.

•       Fatigue: a moderate reduction in fatigue matters to patients, but the trials are small and unblinding is possible, so the effect size is uncertain.

•       Dose and tolerability: if a lower dose or alternate-day regimen produces similar benefit with fewer side effects, adherence and real-world effectiveness may improve. That can matter more than small differences in absorption.

•       Form choice: ferrous bisglycinate may be a sensible option for people who cannot tolerate ferrous sulfate, but there is no strong evidence that it produces better clinical outcomes than a well-tolerated, correctly dosed ferrous sulfate regimen.

13. Conflicts of Interest and Funding

Funding sources need attention, particularly for branded ingredients.

•       Public and academic funding: Cochrane reviews, WHO guidance and many pregnancy and child trials are funded by governments, universities or international agencies.

•       Industry funding: some trials of specific products, including some ferrous bisglycinate studies, were funded or conducted by the ingredient developer or by authors associated with it. One example is the 2001 pediatric study co-authored by an Albion Laboratories founder.

•       Pharmaceutical funding: trials of intravenous iron products are typically sponsored by manufacturers.

•       Independent replication: growing for bisglycinate, but still limited.

Industry involvement does not make results wrong, but independent replication increases confidence. Claims of superior absorption or clinical benefit for a branded iron form should be judged against independent data.

14. Consistency Across Trials

Consistency is high for the main effect and lower for secondary claims.

•       Highly consistent: iron improves hemoglobin and ferritin in deficient people across pregnant women, children and menstruating women, across countries and across iron forms.

•       Fairly consistent: gastrointestinal side effects occur more often with ferrous sulfate than with placebo, and gentler regimens reduce them.

•       Moderately consistent: fatigue improvement in non-anemic iron deficiency.

•       Inconsistent: cognitive and developmental benefits, athletic performance and symptom outcomes in chronic disease.

•       Context-dependent: safety findings in malaria-endemic areas and oral versus intravenous results in heart failure.

Heterogeneity in baseline iron status explains much of the variability. Trials enrolling clearly deficient participants tend to show benefit, while trials enrolling mixed or replete populations tend to show little.

15. Meta-Analyses and Systematic Reviews

Review	Question	Key conclusion
Pena-Rosas et al., 2015 (Cochrane)	Daily iron in pregnancy	Reduces maternal anemia and iron deficiency; probable benefit for birth weight; more side effects
Low et al., 2016 (Cochrane)	Daily iron in menstruating women	Reduces anemia; improves physical performance and some cognitive measures
Pasricha et al., 2013	Iron in children 4–23 months	Improves hemoglobin and reduces anemia and iron deficiency
Neuberger et al., 2016 (Cochrane)	Iron for children in malaria-endemic areas	No increase in clinical malaria when malaria care is provided
Houston et al., 2018	Iron in non-anemic iron deficiency	Reduces fatigue
Tolkien et al., 2015	Ferrous sulfate side effects	Significantly more GI adverse events than placebo
Burden et al., 2015	Iron in non-anemic iron-deficient athletes	Improves iron status; performance results inconsistent
Fischer et al., 2023	Ferrous bisglycinate	Better hemoglobin in pregnancy and fewer GI events; evidence elsewhere limited

 

These reviews give high confidence in the hematological benefit of iron, moderate confidence in some symptom benefits and cautious conclusions about form-specific advantages.

16. Evidence Grading

The grades are an editorial summary, not a formal GRADE assessment. They reflect the number, size and independence of trials, consistency, directness and risk of bias.

Outcome	Grade	Reason
Correction of iron deficiency anemia	High	Many consistent randomized trials and Cochrane reviews
Prevention of anemia in pregnancy	High	Large Cochrane analysis; consistent direction
Improved birth weight	Moderate	Meta-analytic support; some heterogeneity
Reduced anemia in children	High	Consistent reviews
Cognitive and developmental benefit	Low	Inconsistent and short-term trials
Fatigue reduction in non-anemic iron deficiency	Moderate	Pooled benefit; small trials and unblinding risk
Athletic performance	Low	Mixed results; benefit mainly in deficiency
Restless legs symptoms with oral iron	Low	Limited, low-quality trials
Oral iron in heart failure	Low (no benefit shown)	Negative large trial; IV iron works differently
Fewer GI effects with ferrous bisglycinate	Moderate	Consistent trials and meta-analysis; blinding and bias concerns
Lower dose of bisglycinate equals higher dose of sulfate in pregnancy	Moderate	Randomized trial support; replication needed
Alternate-day dosing improves absorption	Moderate (absorption), Low (clinical outcomes)	Isotope studies; fewer long-term trials
Benefit in iron-replete people	None demonstrated	No supportive trials

 

17. Limitations

•       Surrogate outcomes: hemoglobin and ferritin dominate, and symptoms and clinical outcomes are less often measured.

•       Ferritin interpretation: ferritin rises with inflammation, which can mask deficiency or mislead interpretation.

•       Baseline heterogeneity: pooling deficient and replete people dilutes effects.

•       Unblinding: side effects and dark stools can reveal allocation.

•       Form comparisons: head-to-head trials of iron forms are fewer and smaller than trials versus placebo.

•       Industry involvement: funding links in some branded-ingredient trials.

•       Short duration: limited long-term safety and development data.

•       Generalizability: underrepresentation of men, older adults, and people with chronic disease on oral iron.

•       Publication bias: positive small trials are more likely to be published.

•       This review itself: narrative synthesis without a new formal search, so some relevant trials may be missing and details should be checked against sources.

18. Bottom-Line Interpretation

Human research supports oral iron as an effective treatment and prevention strategy for iron deficiency and iron deficiency anemia, particularly in pregnancy, early childhood and menstruating women. The effect on hemoglobin and ferritin is reliable. Effects on fatigue in non-anemic deficiency are plausible and moderately supported. Claims that go beyond deficiency, such as general energy, athletic enhancement or cognitive boosting in people with normal iron status, lack evidence.

Regarding forms, ferrous sulfate remains the evidence-rich reference. Ferrous bisglycinate has reasonable evidence for similar efficacy at lower doses in pregnancy and for fewer gastrointestinal complaints, but more independent, larger trials are needed before declaring it clinically superior. Dosing strategy also matters: lower doses and alternate-day schedules may improve absorption and tolerability.

Practical takeaways are straightforward. Test before supplementing. Match the dose and form to the person and the clinical situation. Recheck blood tests to confirm response. Avoid iron when stores are adequate or in iron overload conditions. Keep iron away from children. Use intravenous iron when oral iron fails or is not appropriate, as in heart failure or severe malabsorption.

This article is educational and is not medical advice.

19. References

References were compiled for educational purposes. Readers should verify details against the original publications.

1.      Anker SD, Comin Colet J, Filippatos G, et al. Ferric carboxymaltose in patients with heart failure and iron deficiency. N Engl J Med. 2009;361(25):2436-2448.

2.      Burden RJ, Morton K, Richards T, Whyte GP, Pedlar CR. Is iron treatment beneficial in iron-deficient but non-anaemic (IDNA) endurance athletes? A systematic review and meta-analysis. Br J Sports Med. 2015;49(21):1389-1397.

3.      Duque X, Martinez H, Vilchis-Gil J, et al. Effect of supplementation with ferrous sulfate or iron bis-glycinate chelate on ferritin concentration in Mexican schoolchildren: a randomized controlled trial. Nutr J. 2014;13:71.

4.      Fischer JAJ, Cherian AM, Bone JN, Karakochuk CD. The effects of oral ferrous bisglycinate supplementation on hemoglobin and ferritin concentrations in adults and children: a systematic review and meta-analysis of randomized controlled trials. Nutr Rev. 2023;81(8):904-920.

5.      Haider BA, Olofin I, Wang M, et al. Anaemia, prenatal iron use, and risk of adverse pregnancy outcomes: systematic review and meta-analysis. BMJ. 2013;346:f3443.

6.      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.

7.      Larson LM, Phiri KS, Pasricha SR. Iron and cognitive development: what is the evidence? Ann Nutr Metab. 2017;71(Suppl 3):25-38.

8.      Lewis GD, Malhotra R, Hernandez AF, et al. Effect of oral iron repletion on exercise capacity in patients with heart failure with reduced ejection fraction and iron deficiency: the IRONOUT HF randomized clinical trial. JAMA. 2017;317(19):1958-1966.

9.      Low MSY, Speedy J, Styles CE, De-Regil LM, Pasricha SR. Daily iron supplementation for improving anaemia, iron status and health in menstruating women. Cochrane Database Syst Rev. 2016;4:CD009747.

10.   Milman N, Jonsson L, Dyre P, Pedersen PL, Larsen LG. Ferrous bisglycinate 25 mg iron is as effective as ferrous sulfate 50 mg iron in the prophylaxis of iron deficiency and anemia during pregnancy in a randomized trial. J Perinat Med. 2014;42(2):197-206.

11.   Moretti D, Goede JS, Zeder C, et al. Oral iron supplements increase hepcidin and decrease iron absorption from daily or twice-daily doses in iron-depleted young women. Blood. 2015;126(17):1981-1989.

12.   Neuberger A, Okebe J, Yahav D, Paul M. Oral iron supplements for children in malaria-endemic areas. Cochrane Database Syst Rev. 2016;2:CD006589.

13.   Pasricha SR, Hayes E, Kalumba K, Biggs BA. Effect of daily iron supplementation on health in children aged 4-23 months: a systematic review and meta-analysis of randomised controlled trials. Lancet Glob Health. 2013;1(2):e77-e86.

14.   Pasricha SR, Tye-Din J, Muckenthaler MU, Swinkels DW. Iron deficiency. Lancet. 2021;397(10270):233-248.

15.   Pena-Rosas JP, De-Regil LM, Garcia-Casal MN, Dowswell T. Daily oral iron supplementation during pregnancy. Cochrane Database Syst Rev. 2015;(7):CD004736.

16.   Pineda O, Ashmead HD. Effectiveness of treatment of iron-deficiency anemia in infants and young children with ferrous bis-glycinate chelate. Nutrition. 2001;17(5):381-384.

17.   Rimon E, Kagansky N, Kagansky M, et al. Are we giving too much iron? Low-dose iron therapy is effective in octogenarians. Am J Med. 2005;118(10):1142-1147.

18.   Sazawal S, Black RE, Ramsan M, et al. Effects of routine prophylactic supplementation with iron and folic acid on admission to hospital and mortality in preschool children in a high malaria transmission setting: community-based, randomised, placebo-controlled trial. Lancet. 2006;367(9505):133-143.

19.   Stoffel NU, Cercamondi CI, Brittenham G, et al. 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. Lancet Haematol. 2017;4(11):e524-e533.

20.   Stoffel NU, Zeder C, Brittenham GM, Moretti D, Zimmermann MB. Iron absorption from supplements is greater with alternate day than with consecutive day dosing in iron-deficient anemic women. Haematologica. 2020;105(5):1232-1239.

21.   Tolkien Z, Stecher L, Mander AP, Pereira DIA, Powell JJ. Ferrous sulfate supplementation causes significant gastrointestinal side-effects in adults: a systematic review and meta-analysis. PLoS One. 2015;10(2):e0117383.

22.   Trotti LM, Becker LA. Iron for the treatment of restless legs syndrome. Cochrane Database Syst Rev. 2019;1:CD007834.