Iron and Improved Iron Levels

Research synthesisLow evidenceModerate effect4 studies · 3 beneficial · 0 neutral · 1 harmful

Across 4 studies, 3 reported beneficial effects of iron supplementation on improving iron levels, with moderate effect sizes observed in the largest meta-analysis of healthy blood donors (Hb: MD 2.52 g/L, ferritin: MD 12.39 ng/mL). One harmful effect was found in a meta-analysis of vitiligo patients, where serum iron was significantly higher. The most studied dose range was 7 to 105 mg/day elemental iron, and the evidence is dominated by moderate effect sizes, though results vary by population.

Effective dose range: 7 to 105 mg/day elemental iron
Studied populations: healthy blood donors, pregnant women, patients with pulmonary hypertension

Caveats: Evidence base is small (only 4 studies) — conclusions should be considered preliminary. Available evidence is overwhelmingly positive (3 of 4 studies beneficial) — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). One study in vitiligo patients reported a harmful association, indicating that benefits may not generalize to all clinical populations.

Generated Jun 16, 2026

Doses used in studies

Elemental Iron · mg/day: 7–105 (median 56, IQR 7–105) — 1 study
mg/day: 4.2 (median 4.2, IQR 4.2–4.2) — 1 study

Safety in these studies

abdominal painIncreased riskRR 1.69, 95% CI 1.15 to 2.47
More participants may experience adverse events with oral iron compared to no iron, including abdominal pain, constipation, and diarrhoea (RR 1.69, 95% CI 1.15 to 2.47; 8 studies, 2641 participants)
from: Oral or parenteral iron supplementation to reduce deferral, iron deficiency and/or anaemia
constipationIncreased riskRR 1.69, 95% CI 1.15 to 2.47
More participants may experience adverse events with oral iron compared to no iron, including abdominal pain, constipation, and diarrhoea (RR 1.69, 95% CI 1.15 to 2.47; 8 studies, 2641 participants)
from: Oral or parenteral iron supplementation to reduce deferral, iron deficiency and/or anaemia
diarrhoeaIncreased riskRR 1.69, 95% CI 1.15 to 2.47
More participants may experience adverse events with oral iron compared to no iron, including abdominal pain, constipation, and diarrhoea (RR 1.69, 95% CI 1.15 to 2.47; 8 studies, 2641 participants)
from: Oral or parenteral iron supplementation to reduce deferral, iron deficiency and/or anaemia
Overall tolerabilityReported
In all included studies, the iron replacement was tolerated well with no serious adverse events.
from: Efficacy of iron replacement in pulmonary hypertension: A systematic review.
weaknessReported
There may be no difference in reported non-gastrointestinal symptoms, except a feeling of 'weakness', which was reduced with oral iron supplements.
from: Oral or parenteral iron supplementation to reduce deferral, iron deficiency and/or anaemia

4 of 4 papersPopulation:

Oral or parenteral iron supplementation to reduce deferral, iron deficiency and/or anaemia in blood donors.
- 2026-06-04
- Meta-Analysis · n = 7,475
- The Cochrane database of systematic reviews 2026(6)
- - Louise J Geneen
  - Karyna Atha
  - Catherine Kimber
  - William McClune
  - Carolyn Dorée
  - Chiara Vendramin
  - Lian Wea Chia
  - David J Roberts
- PubMed: 42240175
- DOI: 10.1002/14651858.cd009532.pub3
3 Insights on
- Improved Iron Levels
- High evidence
- Adults
Hb and ferritin may also be improved with oral iron supplementation compared to no iron (Hb: mean difference (MD) 2.52, 95% CI 0.77 to 4.26 g/L higher; 14 studies, 1940 participants; ferritin: MD 12.39, 95% CI 8.16 to 16.62 ng/mL higher; 8 studies, 1335 participants), but the evidence is very uncertain.
Effect
Beneficial
Effect size
Moderate
Significant
Yes
Dose
variable (7 to 105 mg/day elemental iron)
Healthy lifestyle choices: new insights into vitiligo management.
- 2024-11-18
- Meta-Analysis · n = 542
- Frontiers in immunology 15
- - Xin Liang
  - Fei Guo
  - Qian Fan
  - Xiaoce Cai
  - Jiao Wang
  - Jiale Chen
  - Fang Liu
  - Yuhua Du
  - Yan Chen
  - Xin Li
- PubMed: 39624091
- DOI: 10.3389/fimmu.2024.1440705
8 Insights on
- Improved Iron Levels
- High evidence
- Clinical
The serum iron level of the vitiligo group was significantly higher than that of the control group (MD, 1.181; 95% CI, 0.390-1.972; p <0.005).
Effect
Harmful
Effect size
Moderate
Significant
Yes
The effect of Lactiplantibacillus plantarum 299v together with a low dose of iron on iron status in healthy pregnant women: A randomized clinical trial
- 2021-04-21
- RCT
- Acta Obstetricia et Gynecologica Scandinavica 100(9)
- - U. Axling
  - G. Önning
  - Titti Martinsson Niskanen
  - N. Larsson
  - S. Hansson
  - L. Hulthén
- PubMed: 33880752
- DOI: 10.1111/aogs.14153
17 Insights on
- Improved Iron Levels
- High evidence
- Pregnant Women
Intake of Lp attenuated the decrease in serum ferritin from baseline to week 28 (p = 0.003) and week 35 (p ˂ 0.001) and resulted in reduced prevalence of iron deficiency (59% vs 78%, p = 0.017) and iron deficiency anemia (7.4% vs 21%, p = 0.023) at week 35.
Effect
Beneficial
Effect size
Large
Significant
Yes
Dose
1010 colony forming units twice daily
Efficacy of iron replacement in pulmonary hypertension: A systematic review.
- 2024-12-23
- Systematic Review
- Nutrition and health 31(2)
- - Tejaswini Baral
  - Pravachana Malakapogu
  - Zuha Shyma
  - Shilia Jacob Kurian
  - Ruby Benson
  - Mohan K Manu
  - Debasis Bagchi
  - Sonal Sekhar Miraj
- PubMed: 39711168
- DOI: 10.1177/02601060241303814
4 Insights on
- Improved Iron Levels
- High evidence
- Clinical
We observed an improvement in the six-minute walk distance (6MWD) test, iron indices, peak oxygen intake, and anaerobic threshold after the iron replacement.
Effect
Beneficial
Effect size
Small
Significant
Yes

Iron and Improved Iron Levels

Oral or parenteral iron supplementation to reduce deferral, iron deficiency and/or anaemia in blood donors.

Healthy lifestyle choices: new insights into vitiligo management.

The effect of Lactiplantibacillus plantarum 299v together with a low dose of iron on iron status in healthy pregnant women: A randomized clinical trial

Efficacy of iron replacement in pulmonary hypertension: A systematic review.