Vitamin
B-Complex
A group of eight B vitamins that work together to support energy metabolism, nervous system function, and red blood cell production.
Moderate Evidence
Strong Evidence Mineral
Iron
An essential mineral required for oxygen transport in blood and energy production, commonly supplemented for anemia.
Updated February 20, 2026This content is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication regimen.
Benefits & Uses
- Corrects iron deficiency and iron-deficiency anemia (IDA): Strong evidence from numerous RCTs and meta-analyses that oral or IV iron increases hemoglobin and ferritin and improves anemia-related symptoms.
- Pregnancy: Strong evidence (systematic reviews/meta-analyses) that routine iron or iron–folic acid reduces maternal anemia and iron deficiency, and modestly reduces risk of low birth weight and preterm birth.
- Chronic kidney disease (CKD) anemia: Strong evidence that IV iron improves hemoglobin and reduces erythropoiesis-stimulating agent (ESA) needs; oral iron is often insufficient in moderate-to-severe CKD.
- Heart failure with iron deficiency: Moderate-to-strong evidence that IV iron (especially ferric carboxymaltose) improves functional class, exercise capacity, quality of life, and may reduce heart failure hospitalizations; oral iron is often ineffective.
- Restless legs syndrome (RLS) with low ferritin: Moderate evidence (systematic reviews) that oral or IV iron improves RLS severity in iron-deficient individuals.
- Fatigue in iron-deficient, non-anemic women: Moderate evidence from RCTs that oral iron reduces fatigue when ferritin is low.
- Inflammatory bowel disease (IBD) with IDA: Strong evidence that IV iron is effective and often better tolerated than oral iron when disease is active or oral iron is not tolerated.
- Cognitive/developmental outcomes in infants/children with IDA: Moderate evidence that treating IDA improves cognitive and psychomotor outcomes; benefits in iron-replete children are not established.
Side Effects & Precautions
- Common (10–30% with oral forms): Gastrointestinal upset (nausea, epigastric pain), constipation, diarrhea, heartburn, metallic taste; dark/black stools are expected and harmless. Liquid iron can stain teeth.
- Less common: Vomiting, abdominal cramping, headache. Esophagitis/ulceration if tablets lodge in the esophagus (take with water; avoid lying down immediately after).
- Dose/formulation dependent: GI effects more likely with higher elemental iron doses and when taken on an empty stomach; slow-release and lower/alternate-day dosing may improve tolerance.
- IV iron adverse effects: Infusion reactions (flushing, chest/back pain, hypotension) typically mild/transient (~1–3%); serious hypersensitivity/anaphylaxis is rare (<0.1%) with modern preparations but reported—higher with older high–molecular-weight dextran (largely discontinued). Extravasation can cause long-lasting skin staining. Ferric carboxymaltose can cause hypophosphatemia (biochemical in a substantial proportion; symptomatic cases uncommon but possible, especially with repeated dosing).
- Rare but serious: Acute iron poisoning/overdose (especially in children) with risk of metabolic acidosis, shock, hepatic failure; iron overload with chronic excessive intake or in genetic/secondary iron-loading conditions causing liver, endocrine, and cardiac injury.
- Infection risk: Because iron can promote bacterial growth, high-dose IV iron during active severe infection is used cautiously; RCTs show mixed results on infection risk.
Dosage & Administration
- Typical supplemental ranges in studies (elemental iron, not salt weight):
- Iron-deficiency anemia (adults): ~60–200 mg/day, often divided; newer studies suggest 40–100 mg on alternate days may improve absorption and GI tolerance. Duration guided by labs (restore ferritin/TSAT) plus several months to replenish stores.
- Pregnancy: Commonly 30–60 mg/day prophylactically; higher doses used to treat confirmed IDA per clinician guidance.
- Restless legs syndrome with low ferritin: Oral regimens similar to IDA or single/total-dose IV iron used in trials; target ferritin typically >75–100 µg/L.
- CKD/IBD/heart failure with iron deficiency: IV iron is frequently used; dosing depends on product and iron deficit (e.g., ferric carboxymaltose 500–1000 mg per session; iron sucrose ~200 mg per session, repeated). Total dose calculated from weight, hemoglobin, and ferritin/TSAT.
- Formulations: Ferrous salts (sulfate, gluconate, fumarate) are common; elemental iron content varies by salt. Taking with vitamin C or a source of ascorbic acid may enhance non-heme iron absorption, while calcium, tea/coffee, and some medications reduce it.
- Note: Optimal dose, schedule, and route vary by individual condition, tolerance, and laboratory parameters; dosing should be personalized and medically supervised, especially for IV iron.
Contraindications
- Iron overload states: Hereditary hemochromatosis, hemosiderosis, repeated transfusions, certain hemolytic/sideroblastic anemias—avoid supplemental iron unless directed by a specialist.
- Anemia not due to iron deficiency (e.g., thalassemia major, B12/folate deficiency) unless iron deficiency is confirmed.
- Known hypersensitivity to a specific IV iron product (contraindication to that formulation).
- Active severe infection: Use caution with IV iron; defer until infection is controlled unless compelling indication.
- GI disorders: Active peptic ulcer disease or severe gastritis—oral iron may exacerbate symptoms; consider alternative routes. In IBD flares, IV iron is often preferred.
- Pediatric safety: High risk of accidental overdose—keep out of reach of children; use childproof containers.
- Pregnancy and breastfeeding: Generally considered safe and commonly recommended when deficiency is present; avoid excessive dosing and use under clinician guidance.
- Surgery: Iron does not increase bleeding and is not routinely stopped. Coordinate timing with perioperative antibiotics (fluoroquinolones/tetracyclines) to avoid chelation interactions; IV iron is sometimes used preoperatively to correct anemia. Note that oral iron can darken stools and may confound fecal occult blood testing.
- Laboratory testing: Oral iron close to testing can transiently affect some iron indices; follow pre-test instructions.
Known Interactions
| Substance | Type | Severity | Description |
|---|---|---|---|
| Levothyroxine | antagonistic | moderate | Iron forms insoluble complexes in the gut, reducing levothyroxine absorption and efficacy; separate dosing and monitor TSH. |
| Fluoroquinolone antibiotics (e.g., ciprofloxacin, levofloxacin) | antagonistic | severe | Chelation with iron markedly reduces antibiotic absorption; administer fluoroquinolones several hours apart from iron. |
| Tetracyclines (e.g., doxycycline) | antagonistic | moderate | Iron chelates tetracyclines, lowering antibiotic exposure; separate dosing by at least 2–4 hours. |
| Bisphosphonates (e.g., alendronate) | antagonistic | moderate | Concurrent iron reduces bisphosphonate absorption; take on an empty stomach separate from iron and other minerals. |
| Levodopa/carbidopa | antagonistic | moderate | Iron can chelate levodopa and reduce its absorption and clinical effect; separate dosing and monitor symptom control. |
| Methyldopa | antagonistic | moderate | Iron may reduce methyldopa absorption and antihypertensive effect; avoid coadministration and monitor blood pressure. |
| Calcium supplements/antacids (e.g., calcium carbonate, aluminum/magnesium hydroxide) | antagonistic | moderate | Increase gastric pH or compete with iron, reducing iron absorption; separate by several hours. |
| Dimercaprol (BAL) | caution | severe | Forms nephrotoxic complexes with iron; avoid concurrent use (contraindicated). |
Sources
- Daily oral iron supplementation during pregnancy: Cochrane systematic review and meta-analysis (meta-analysis) , 2015
- Iron for the treatment of restless legs syndrome: Cochrane Review (meta-analysis) , 2019
- Intravenous iron therapy in heart failure with iron deficiency: meta-analysis of randomized trials (meta-analysis) , 2019
- Oral iron for unexplained fatigue in non-anemic women with low ferritin: randomized controlled trial (rct) , 2012
- Oral versus intravenous iron for anemia in inflammatory bowel disease: systematic review and meta-analysis (meta-analysis) , 2013
- Intravenous versus oral iron for anemia management in chronic kidney disease: systematic review and meta-analysis (meta-analysis) , 2016
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Mineral
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Moderate Evidence
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This content is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication regimen.