Iron
Iron (Various Forms)
Essential mineral for oxygen transport and energy production — critical for those with deficiency, especially women and athletes.
Iron is essential for hemoglobin production, oxygen transport, and cellular energy. Deficiency is the most common nutritional deficiency worldwide, affecting energy, cognition, immunity, and exercise performance. Different forms vary greatly in absorption and tolerability. Only supplement if deficient or at risk — excess iron causes oxidative damage.
Mechanisms of Action
Oxygen Transport
Essential component of hemoglobin
Energy Production
Required for mitochondrial function
Recommended Dose
18-45mg elemental iron for deficiency (varies by severity)
Loading: Every-other-day dosing may improve absorption
Optimal Timing
- On empty stomach if tolerated
- Away from tea, coffee, dairy
Can be taken without food
Best Form
Ferrous bisglycinate (gentle, well-absorbed) or iron protein succinylate
Alternatives: Ferrous sulfate (cheapest but harsh), Ferrous fumarate, Heme iron (from animal source)
Bisglycinate causes less GI upset. Ferrous sulfate is effective but causes more constipation. Check 'elemental iron' content, not total weight.
Duration
Minimum: 12 weeks
Optimal: 24 weeks
Cycling: Continue 3-6 months after ferritin normalizes, then retest. Do NOT supplement long-term without monitoring.
Note: Best absorbed on empty stomach with vitamin C. If GI upset, take with small amount of food. Avoid taking with calcium, tea, coffee within 2 hours.
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Energy Restoration
Improved energy levels when deficient
Cognitive Function
Better focus and mental clarity
Exercise Performance
Improved endurance capacity
Higher needs (27mg/day); follow prenatal guidance
Lower risk of deficiency — test before supplementing
Who Should NOT Take This
- Hemochromatosis or iron overload
- Repeated blood transfusions
- Adequate iron stores (test first!)
Drug Interactions
Reduce iron absorption
Reduces absorption — take 4+ hours apart
Iron reduces antibiotic absorption — separate by 2+ hours
Reduced levodopa effectiveness, worsening Parkinson symptoms
Significantly reduced antibiotic effectiveness
Reduced drug effectiveness for osteoporosis
Up to 90% reduction in antibiotic absorption
Antibiotic treatment failure
Counteracts therapeutic effect of iron chelation
Possible Side Effects
Tip: Use bisglycinate form; add magnesium; increase fiber/water
Tip: Take with food; switch to gentler form
Tip: Normal effect of iron — not concerning
Warnings
- ALWAYS test iron levels before supplementing — excess iron is harmful
- Keep away from children — iron overdose is dangerous
- Do NOT take with calcium, tea, or coffee
- Monitor ferritin to avoid iron overload
Top studies from 40+ peer-reviewed papers
Anker SD et al. • Nature medicine (2025)
“This meta-analysis examined the effects of Iron.”
Key Findings:
- All-cause mortality at 12 months and for the complete length of follow-up (HR = 0.82 (95% CI = 0.65-1.03)) and HR = 0.92 (95% CI = 0.80-1.07), respectively, indicated the overall safety of i.v. iron treatment.
- These findings suggest that treating iron deficiency in patients with HF significantly reduces cardiovascular events and also suggests further investigation of optimal dosing of i.v. iron.© 2025.
- Treatment effects were greatest in the first year after randomization when the doses of i.v. iron provided are highest.
Finkelstein JL et al. • The Cochrane database of systematic reviews (2024)
“Daily oral iron supplementation during pregnancy may reduce maternal anaemia and iron deficiency at term.”
Key Findings:
- There is probably little to no difference in maternal death (2 versus 4 events, RR 0.57, 95% CI 0.12 to 2.69; 3 trials, 14,060 women; moderate-certainty evidence).
- Infant outcomes: Women taking iron supplements are probably less likely to have infants with low birthweight (5.2% versus 6.1%; RR 0.84, 95% CI 0.72 to 0.99; 12 trials, 18,290 infants; moderate-certainty evidence), compared to placebo or no iron supplementation.
- However, the evidence is very uncertain for infant birthweight (MD 24.9 g, 95% CI -125.81 to 175.60; 16 trials, 18,554 infants; very low-certainty evidence).
- The evidence is very uncertain about the effects of iron + folic acid on maternal iron-deficiency anaemia (10.8% versus 25%; RR 0.43, 95% CI 0.17 to 1.09; 1 trial, 131 women; very low-certainty evidence), or maternal deaths (no events; 1 trial; very low-certainty evidence).
Zhou Y et al. • Nutrients (2024)
“It was found that dietary factors were one of the major causes of anemia, and iron-containing supplements and nutrition counseling could be effective interventions to reduce the prevalence of anemia, ID, and IDA among Chinese pregnant women.”
Key Findings:
- The results showed that the prevalence of anemia, ID, and IDA among pregnant women in China were 30.7% (95% CI: 26.6%, 34.7%), 45.6% (95% CI: 37.0%, 54.2%), and 17.3% (95% CI: 13.9%, 20.7%), respectively.
- Generally, lower prevalence was observed in the economically more advanced eastern region of the country, while the prevalence of ID was higher in the eastern region than that in the western region.
- The prevalence of anemia and IDA in rural areas was higher than that in urban areas, but ID prevalence was higher in urban areas.
- In conclusion, the regional differences and urban-rural disparities in the prevalence of anemia indicate the need for more context-specific interventions to prevent and treat anemia.
Jensen MCH et al. • The Cochrane database of systematic reviews (2024)
“Intravenous iron probably reduces fatigue slightly in the early postpartum weeks (8 to 28 days) compared to oral iron tablets, but probably results in little to no difference after four weeks.”
Key Findings:
- Intravenous iron versus oral iron supplementation The evidence is very uncertain about the effect of intravenous iron on mortality (risk ratio (RR) 2.95, 95% confidence interval (CI) 0.12 to 71.96; P = 0.51; I² = not applicable; 3 RCTs; 1 event; 572 women; very low-certainty evidence).
- Intravenous iron probably results in a slight reduction in fatigue within 8 to 28 days (standardised mean difference -0.25, 95% CI -0.42 to -0.07; P = 0.006; I² = 47%; 2 RCTs; 515 women; moderate-certainty evidence).
- Oral iron probably increases the risk of constipation compared to intravenous iron (RR 0.12, 95% CI 0.06 to 0.21; P < 0.001; I² = 0%; 10 RCTs; 1798 women; moderate-certainty evidence).
- The evidence is very uncertain about the effect of intravenous iron on anaphylaxis or hypersensitivity (RR 2.77, 95% CI 0.31 to 24.86; P = 0.36; I² = 0%; 12 RCTs; 2195 women; very low-certainty evidence).
Shah AA et al. • JAMA network open (2021)
“In this large systematic review and meta-analysis, intravenous iron was associated with an increased risk of infection.”
Key Findings:
- Intravenous iron was associated with an increased risk of infection when compared with oral iron or no iron (RR, 1.17; 95% CI, 1.04-1.31; I2 = 37%; moderate certainty of evidence).
- In this large systematic review and meta-analysis, intravenous iron was associated with an increased risk of infection.
- Well-designed studies, using standardized definitions of infection, are required to understand the balance between this risk and the potential benefits.
Study Type Distribution
Goals This Supplement Supports
Related Goals
This information is for educational purposes only and is not intended as medical advice. Always consult a qualified healthcare provider before starting any supplement.