Iron
Fe (Ferrous / Ferric Forms)
Key Benefits
Energy & Vitality
Critical for hemoglobin synthesis, enabling red blood cells to transport oxygen throughout the body.
Cognitive Function
Supports brain oxygenation and neurotransmitter synthesis, preventing brain fog and poor concentration.
Physical Performance
Required for myoglobin in muscles, supporting endurance and strength.
Immune Support
Essential for immune cell proliferation and function.
Activation Synergies
Vitamin C (ascorbic acid) converts iron to more absorbable ferrous form and prevents precipitation in the gut.
Recommended Dosage
medical_servicesOnly supplement if deficiency is confirmed via blood work (ferritin, serum iron, TIBC). Ferrous forms (sulfate, gluconate, bisglycinate) absorb better than ferric. Take with vitamin C to enhance absorption; avoid with calcium, tea, or coffee. Start low to assess tolerance.
Deficiency Indicators
- Severe fatigue and weakness
- Pale skin, nail beds, or inner eyelids
- Shortness of breath or rapid heartbeat
- Cold hands and feet
- Brittle nails or hair loss
- Restless leg syndrome
- Pica (craving ice or non-food items)
Scientific Citations
Iron Fact Sheet for Health Professionals
Iron: Research Summary
Forms & absorption
scienceNot all forms absorb equally — these are ordered best-absorbed first.
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Ferrous bisglycinate trending_up Well absorbed · best for Sensitive stomachs
Chelated form — well absorbed with noticeably less nausea and constipation than iron salts.
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Ferrous sulfate trending_flat Moderate · best for Correcting deficiency cheaply
The standard, effective and inexpensive, but commonly causes constipation or nausea.
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Ferrous gluconate trending_flat Moderate
Gentler than sulfate but carries less elemental iron per tablet, so doses run larger.
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Ferric (non-heme) salts trending_down Poorly absorbed
Ferric forms absorb far less well than ferrous ones.
Absorption varies between people; informational only, not medical advice.
Research & Sources
What the evidence says — with links to the original studies
There is strong, authoritative consensus that oral iron supplementation is effective and warranted for treating and preventing confirmed iron deficiency and iron-deficiency anemia, but it should not be taken routinely without a documented need because of common GI side effects. Ferrous (Fe2+) salts are more bioavailable than ferric (Fe3+) salts, and controlled-isotope studies (Stoffel/Moretti) show that lower or alternate-day dosing raises fractional absorption by transiently lowering hepcidin. Vitamin C reliably enhances non-heme iron absorption in isolated studies, but a randomized clinical trial found it adds no meaningful clinical benefit over iron alone for treating anemia. Newer chelated forms such as ferrous bisglycinate show comparable or better efficacy at lower elemental doses with fewer GI complaints in some populations.
Supporting Evidence
Authoritative reference. States ferrous iron is more bioavailable than ferric iron; ascorbic acid enhances non-heme absorption; high doses (>=45 mg/day) cause GI upset; lists groups at risk of deficiency who may warrant supplementation.
Alternate-day dosing gave higher fractional absorption (21.8% vs 16.3%) and greater cumulative absorption; daily and twice-daily dosing raised hepcidin, suppressing next-dose absorption.
Extends findings to anemic (not just depleted) women; fractional absorption 40-50% higher on alternate days; hepcidin rise persists ~24h, suppressing absorption the following day.
57 trials, 48,971 women. Iron probably reduces maternal iron-deficiency anemia at term (moderate-certainty); reductions in anemia and iron deficiency were low-certainty.
43 RCTs, 6,831 adults. Ferrous sulfate roughly doubled GI side effects vs placebo (OR 2.32, 95% CI 1.74-3.08); no significant dose-response, so lower doses did not clearly reduce risk.
Iron alone was equivalent to iron plus vitamin C for hemoglobin and ferritin response; concluded vitamin C is not essential when treating IDA with oral iron.
In pregnant women, ferrous bisglycinate raised hemoglobin more than comparators (often ferrous sulfate) at lower elemental doses, with fewer GI side effects (IRR 0.36); no clear benefit in children.
Opposing / Critical Views
Opposes the common claim that co-administered vitamin C meaningfully improves clinical outcomes of oral iron therapy; found no added clinical benefit over iron alone.
Full-text & official documents
Educational summary of published research — not medical advice. Consult a qualified professional before supplementing.
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