What dose of elemental iron should be prescribed three times a week for iron supplementation?

Iron Supplementation Three Times Per Week

For three-times-per-week iron supplementation, prescribe 100-200 mg of elemental iron per dose (e.g., one 325 mg ferrous sulfate tablet containing 65 mg elemental iron, or one 322 mg ferrous fumarate tablet containing 106 mg elemental iron) on non-consecutive days such as Monday-Wednesday-Friday. 1, 2, 3

Why Three Times Per Week Is Suboptimal

The evidence strongly favors alternate-day dosing (every other day) over three-times-weekly dosing because:

• Iron doses ≥60 mg stimulate an acute increase in hepcidin that persists for 24 hours but subsides by 48 hours, making alternate-day dosing physiologically superior for maximizing fractional iron absorption 4
• The American Gastroenterological Association recommends once-daily or every-other-day dosing as superior to multiple daily doses, as hepcidin elevation blocks absorption of subsequent doses for 24-48 hours 1, 3
• Alternate-day dosing significantly increases both fractional and total iron absorption compared to daily dosing, and would theoretically be superior to three-times-weekly dosing 1, 2, 4

Recommended Dosing Strategy

If you must prescribe three times per week:

• Prescribe 100-200 mg elemental iron per dose on non-consecutive days (Monday-Wednesday-Friday or similar schedule) 1, 2, 4
• Common formulations include:
  • Ferrous sulfate 325 mg tablet = 65 mg elemental iron 2, 3
  • Ferrous fumarate 322 mg tablet = 106 mg elemental iron 2
  • Ferrous gluconate 325 mg tablet = 35 mg elemental iron (requires multiple tablets) 2

Optimal Administration Instructions

• Take in the morning on an empty stomach (1-2 hours before or after meals) to maximize absorption, as serum hepcidin increases during the day and food reduces absorption by up to 50% 1, 2, 3
• Take with 250-500 mg vitamin C to enhance absorption through chelate formation 1, 3
• Avoid coffee, tea, and calcium-containing foods/medications for at least 1-2 hours before and after the dose, as these significantly inhibit iron absorption 1, 3

Monitoring and Duration

• Check hemoglobin at 4 weeks to assess response; expect an increase of at least 10 g/L (1 g/dL) within 2-4 weeks in responding patients 1, 3
• Continue treatment for approximately 3 months after hemoglobin normalizes to adequately replenish iron stores, not just correct anemia 1, 3
• The absence of hemoglobin rise of at least 10 g/L after 2 weeks strongly predicts treatment failure (sensitivity 90.1%, specificity 79.3%) and warrants reassessment 1, 3

Important Caveats

• Three-times-weekly dosing has no evidence base—the literature supports either daily, alternate-day, or (historically) multiple-times-daily dosing, but not specifically three-times-weekly 1, 2, 3, 4
• If gastrointestinal side effects occur, reduce to alternate-day dosing (every other day) rather than three-times-weekly, as this maintains higher fractional absorption while improving tolerability 1, 2, 3
• Never prescribe multiple doses per day, as this increases side effects without improving absorption due to hepcidin-mediated blockade 1, 3

When to Consider Intravenous Iron

Switch to IV iron if:

• Oral iron causes intolerable gastrointestinal symptoms despite dosing adjustments 1, 3
• Hemoglobin fails to rise after 2-4 weeks of adherent oral therapy 1, 3
• Patient has malabsorption conditions (inflammatory bowel disease, celiac disease, prior gastric surgery) 1, 3
• Rapid correction is needed or blood loss exceeds oral replacement capacity 1, 3