What dose of ascorbic acid (Vitamin C) is recommended to enhance iron absorption in patients taking ferrous sulfate (Iron supplement)?

Recommended Dose of Ascorbic Acid with Ferrous Sulfate

When taking ferrous sulfate for iron deficiency anemia, ascorbic acid (vitamin C) should be added at a molar ratio of at least 2:1 (approximately 20mg of ascorbic acid for every 3mg of elemental iron) to enhance iron absorption. 1, 2

Dosing Recommendations

Standard Dosing

• For meals with low to medium levels of iron absorption inhibitors:
  • 20mg ascorbic acid per 3mg elemental iron (2:1 molar ratio) 2
  • For a standard 65mg elemental iron dose (200mg ferrous sulfate tablet), approximately 400mg ascorbic acid is appropriate

Higher Dosing for Special Situations

• For meals with high levels of iron absorption inhibitors:
  • Molar ratio in excess of 4:1 may be required 2
  • This translates to approximately 800mg ascorbic acid for a 65mg elemental iron dose

Timing Considerations

• Morning administration is optimal for both iron and ascorbic acid 3
• Alternate-day dosing may improve iron absorption compared to daily dosing 1, 4
• Take on an empty stomach, avoiding food within 2 hours before or 1 hour after supplementation 3

Formulations

• Commercial preparations combining ferrous sulfate with ascorbic acid are available 1
• These modified-release tablets typically contain 325mg ferrous sulfate (105mg elemental iron) with ascorbic acid 1

Clinical Benefits of Adding Ascorbic Acid

• Enhances iron absorption by:
  • Converting ferric iron to the more absorbable ferrous form 2
  • Chelating iron to improve solubility 2
• Particularly beneficial in patients with:
  • Poor response to standard iron therapy 1
  • Malabsorption conditions 3
  • Post-gastrectomy status 5

Monitoring Response

• Expect hemoglobin to rise by 2 g/dL after 3-4 weeks of proper supplementation 1
• Absence of hemoglobin rise of at least 10 g/L after 2 weeks strongly predicts treatment failure 3

Important Considerations and Cautions

• Ascorbic acid's effectiveness depends on its stability in the chosen vehicle 2
• Avoid coffee and tea around iron administration as they contain inhibitors of iron absorption 3
• Patients with hemochromatosis should avoid vitamin C supplements due to risk of enhanced iron absorption 6
• Continue iron therapy with ascorbic acid for 3 months after normalization of hemoglobin to ensure adequate repletion of iron stores 1, 3

By following these guidelines for ascorbic acid supplementation with ferrous sulfate, you can optimize iron absorption and improve treatment outcomes for iron deficiency anemia.