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Iron (Various Forms)
Essential mineral for oxygen transport and energy production — critical for those with deficiency, especially women and athletes.
What the evidence says
Iron appears to help in 10 of 14 studies with measurable effects — the evidence leans clearly favourable.
Most evidence is from high-quality meta-analyses and randomised trials published 2012–2026 with a typical study size of 529 participants.
Based on 43 studies · 18 meta-analyses · 10 RCTs · 545,585 total participants
Confidence
HighWhat the studies found
By outcome
See full supplement plans that include Iron.
Iron has an evidence score of 9/10 — very strong evidence based on 43 indexed studies, including 35 meta-analyses. Essential mineral for oxygen transport and energy production — critical for those with deficiency, especially women and athletes.
The commonly studied dose of Iron is 18-45mg elemental iron for deficiency (varies by severity). Research points to an estimated optimal dose around 30mg elemental iron, with a minimum effective dose near 10mg elemental iron. Individual response varies — start low and adjust.
The best time to take Iron is between meals. It can be taken on an empty stomach. Iron absorption is tightly regulated by hepcidin and occurs primarily in the duodenum via DMT1 (non-heme) and HCP1 (heme) transporters.
Zinc
Likely helpsInvolved in 300+ enzymatic reactions — supports immune defense, testosterone production, wound healing, and sleep quality.
Electrolyte Complex
Likely helpsEssential minerals for hydration, muscle function, and performance — crucial for athletes, fasters, and those on low-carb diets.
Last reviewed May 2026 · evidence from 40 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
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.
Essential component of hemoglobin
Required for mitochondrial function
How Iron works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
18-45mg elemental iron for deficiency (varies by severity)
Loading: Every-other-day dosing may improve absorption
Can be taken without food
| Form | Type |
|---|---|
| 💊Ferrous bisglycinate (gentle, well-absorbed) or iron protein succinylate | Recommended |
| 💊Ferrous sulfate (cheapest but harsh) | Alternative |
| 💊Ferrous fumarate | Alternative |
| 💊Heme iron (from animal source) | Alternative |
Bisglycinate causes less GI upset. Ferrous sulfate is effective but causes more constipation. Check 'elemental iron' content, not total weight.
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.
You can get iron from these foods and drinks. Doses are typical per-serving estimates — actual content varies by brand, brew, cooking, etc.
8.1 mg per 3 ozs
3 oz cooked, heme iron — 15–35% absorbed. Non-heme plant iron absorbs much less (~5%).
6.6 mg per cup
1 cup cooked. Iron is non-heme — pair with vitamin C to boost absorption ~3×. Folate is food-folate form; MTHFR-variant carriers convert less efficiently.
17 mg per 3 ozs
3 oz cooked. Preformed retinol (no conversion needed). Don't exceed 1 serving/week if pregnant — vitamin A toxicity risk.
Based on meta-analyses showing hemoglobin improvements of 2.01-5.30 g/dL in iron deficient populations. Higher doses show diminishing returns with increased GI side effects. Effectiveness varies significantly by baseline iron status and form used.
Improved energy levels when deficient
Better focus and mental clarity
Improved endurance capacity
Higher needs (27mg/day); follow prenatal guidance
Lower risk of deficiency — test before supplementing
Reduces absorption — take 4+ hours apart
Reduce iron absorption
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
Tip: Use bisglycinate form; add magnesium; increase fiber/water
Tip: Take with food; switch to gentler form
Tip: Normal effect of iron — not concerning
Vitamin C dramatically increases iron absorption
2-3x better absorption when taken together
All needed for red blood cell production
Complete anemia prevention/treatment
Molybdenum supports iron metabolism and utilization
Better iron utilization and reduced sulfite sensitivity
Lactoferrin-bound iron is absorbed via specific receptors, offering a gentler iron delivery mechanism than ferrous sulfate with fewer GI side effects.
Improved iron bioavailability with reduced GI distress in iron-deficiency anemia
Iron is generally safe at recommended doses, with a few precautions worth noting. The most commonly reported side effects are constipation, nausea/GI upset, dark stools. Use caution if any of these apply to you: Hemochromatosis or iron overload; Repeated blood transfusions; Adequate iron stores (test first!).
Iodine
Mixed evidenceEssential trace mineral for thyroid hormone production — deficiency is common and affects metabolism, energy, and cognition.
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