What enhances ferrous sulfate (iron supplement) absorption?

Enhancing Ferrous Sulfate Absorption

Vitamin C (ascorbic acid) is the most effective enhancer of ferrous sulfate absorption, ideally taken at a dose of 500 mg with iron supplements on an empty stomach. 1, 2

Key Enhancers of Ferrous Sulfate Absorption

• Vitamin C (ascorbic acid) forms a chelate with iron that prevents formation of insoluble iron compounds and reduces ferric to ferrous iron, significantly improving absorption 1, 3
• Taking iron on an empty stomach maximizes absorption, though this may increase gastrointestinal side effects 1, 3
• Consuming iron with meat protein improves absorption by enhancing both heme and non-heme iron uptake 1
• Once-daily dosing is preferable to multiple daily doses, as serum hepcidin increases after iron intake and remains elevated for up to 48 hours, blocking further absorption 1, 3, 4
• Alternate-day dosing may be more effective than consecutive-day dosing, as it allows hepcidin levels to decrease between doses 3, 4

Factors That Inhibit Ferrous Sulfate Absorption

• Tea and coffee are powerful inhibitors of iron absorption and should not be consumed within an hour after taking iron supplements 1, 3
• Calcium-containing foods or supplements can significantly reduce iron absorption 3
• High-fiber meals can decrease iron absorption 1
• Multiple daily doses increase side effects without improving absorption due to hepcidin-mediated regulatory mechanisms 3, 4

Optimal Administration Strategy

• Take ferrous sulfate as a single morning dose of 65 mg elemental iron (one 200 mg tablet) 1, 3
• Take with 500 mg of vitamin C (ascorbic acid) to enhance absorption, even when taken with meals containing calcium or fiber 1, 3
• Administer on an empty stomach if tolerated; if not, taking with meals is acceptable but may reduce absorption 1, 3
• Consider alternate-day dosing rather than daily dosing to optimize absorption 3, 4
• Avoid tea, coffee, and calcium-containing foods or supplements within an hour of taking iron 1, 3

Special Considerations

• Enteric-coated ferrous sulfate tablets should be avoided as they significantly reduce iron absorption (3.5% vs 12% for uncoated tablets) 5
• For patients who cannot tolerate standard ferrous sulfate doses, consider lower doses which may be equally effective and better tolerated 1, 3
• In patients with inflammatory conditions or malabsorption disorders, oral iron absorption may be impaired, and intravenous iron should be considered 1, 3
• Supplemental vitamin C should be avoided in patients with hemochromatosis, as it can accelerate iron deposition and worsen cardiac function 1

Monitoring Response

• Expect hemoglobin to increase by approximately 1 g/dL within 2 weeks in patients responding to therapy 1, 3
• Continue iron supplementation for 3 months after hemoglobin normalizes to ensure adequate repletion of iron stores 1, 3
• If no improvement in hemoglobin is seen after 2-4 weeks of proper oral supplementation, consider alternative approaches such as intravenous iron 1, 3