In an otherwise healthy adult with mild‑to‑moderate iron deficiency and low ferritin, should ferrous gluconate be taken daily or every other day?

Oral Iron Gluconate for Low Ferritin: Daily vs. Alternate-Day Dosing

For an otherwise healthy adult with low ferritin, ferrous gluconate should be taken on alternate days (every other day) rather than daily, using a dose of 100–200 mg elemental iron per dose. This regimen markedly increases fractional iron absorption compared to daily dosing while reducing gastrointestinal side effects. 1, 2

Why Alternate-Day Dosing Is Superior

The physiological basis for alternate-day dosing is hepcidin regulation. When you take oral iron doses ≥60 mg elemental iron, serum hepcidin levels increase and remain elevated for approximately 24 hours, blocking further iron absorption during that period. 1, 2 Taking a second dose within 24 hours results in a 35–45% reduction in absorption from that second dose due to this hepcidin-mediated blockade. 1, 3

Alternate-day dosing allows hepcidin to subside by 48 hours after the initial dose, thereby restoring full absorptive capacity for the next dose. 1, 2 This approach significantly increases fractional iron absorption in iron-depleted individuals compared with daily dosing. 1

Specific Dosing Recommendations for Ferrous Gluconate

Elemental Iron Content

• Each ferrous gluconate 324 mg tablet contains approximately 37–38 mg elemental iron (≈11–12% elemental iron by weight). 1, 3, 4
• The FDA-approved ferrous gluconate formulation provides 38 mg elemental iron per 324 mg tablet. 4

Optimal Regimen

Take 3–5 tablets (approximately 114–190 mg elemental iron) every other day in the morning on an empty stomach. 1, 3 This provides the target range of 100–200 mg elemental iron per dose recommended for alternate-day supplementation. 1

• If you must take iron with food due to intolerance, co-administer 250–500 mg vitamin C to enhance absorption. 1
• Avoid coffee, tea, or calcium-containing foods/supplements within 1–2 hours of the iron dose, as these inhibit absorption. 1, 3

Why Not Daily Dosing?

Daily dosing of ferrous gluconate would require 2–3 tablets (74–114 mg elemental iron) taken once daily to meet the 50–100 mg elemental iron target. 5, 1 However, this approach:

• Does not improve total iron absorption compared to alternate-day dosing due to hepcidin blockade 1, 2
• Increases gastrointestinal side effects (nausea, constipation, abdominal discomfort) without improving hemoglobin response 1, 3
• Results in lower fractional absorption efficiency 2

Monitoring Your Response

Check hemoglobin 2 weeks after starting therapy. An increase of ≥10 g/L (≥1 g/dL) predicts treatment success with 90% sensitivity and 79% specificity. 1, 3 Failure to achieve this rise strongly predicts treatment failure and warrants evaluation for non-adherence, ongoing blood loss, malabsorption, or concurrent vitamin B12/folate deficiency. 1, 3

Continue supplementation for approximately 3 months after hemoglobin normalizes to fully replenish bone marrow iron stores. 1, 3 Monitor hemoglobin every 6 months during the first year after treatment completion to detect recurrent deficiency. 1, 3

Cost and Practical Considerations

Ferrous gluconate is less concentrated than other ferrous salts, requiring more tablets per dose. 1, 3 It costs approximately $1.50–$3.30 for a 30-tablet supply, compared to $0.30–$4.50 for ferrous sulfate. 3

If cost or pill burden is a concern, consider switching to ferrous sulfate (65 mg elemental iron per 200 mg tablet), which requires only 1–2 tablets every other day to achieve the same 100–200 mg elemental iron target. 1, 3 No oral iron formulation has demonstrated superior efficacy or tolerability; all ferrous salts are therapeutically equivalent. 1, 3

When to Escalate to Intravenous Iron

Switch to IV iron if:

• Hemoglobin does not rise after 2–4 weeks of adherent oral therapy 1, 3
• Gastrointestinal side effects remain intolerable despite alternate-day dosing and taking with food 1, 3
• You have malabsorption syndromes (inflammatory bowel disease, celiac disease, post-bariatric surgery) 1, 3
• Ongoing blood loss exceeds the replacement capacity of oral iron 1

Early oral non-responders have only a 21% chance of later response with continued oral iron versus a 65% response rate with IV iron. 1, 3 Intravenous iron produces a clinically meaningful hemoglobin increase within one week. 1, 3

Common Pitfalls to Avoid

• Do not take multiple doses per day. This increases side effects without improving absorption due to hepcidin blockade. 1, 3
• Do not switch between different ferrous salts expecting better tolerability. Evidence does not support this practice. 5, 1, 3
• Do not discontinue iron when hemoglobin normalizes. Continue for an additional 3 months to restore iron stores. 1, 3
• Do not use multivitamin preparations as your sole iron source. They contain ≤14 mg elemental iron, which is insufficient for treating iron deficiency. 1, 3