How should iron supplements be taken?

Optimal Iron Supplementation Protocol

Iron supplements should be taken once daily in the morning on an empty stomach with vitamin C (80 mg) to maximize absorption, and tea or coffee should be avoided within an hour after taking iron. 1, 2

Oral Iron Formulation Selection

• Ferrous sulfate is the preferred oral iron formulation as it is the least expensive option with no evidence of inferiority to other formulations 1
• Other ferrous salts (gluconate, fumarate) and ferric formulations are equally effective but typically more expensive 1, 3
• If side effects occur with one formulation, trying another formulation may help improve tolerance 2, 3

Optimal Dosing Schedule

• Iron should be taken once daily at most, as more frequent dosing increases side effects without improving absorption 1
• Every-other-day dosing may be better tolerated with similar or equal absorption rates compared to daily dosing 1, 4, 5
• Morning dosing is preferred over afternoon or evening dosing due to circadian variations in hepcidin levels 2, 4

Maximizing Absorption

• Take iron with 80 mg of vitamin C (ascorbic acid) to enhance absorption by forming a chelate with iron and preventing formation of insoluble compounds 1
• Take iron on an empty stomach when possible for optimal absorption 2, 6
• Avoid tea and coffee within an hour after taking iron as they are powerful inhibitors of iron absorption 1, 2
• Avoid taking iron with calcium or fiber-containing foods, which can reduce absorption 2, 6

Managing Side Effects

• Common side effects include constipation (12%), diarrhea (8%), and nausea (11%) 1
• Taking iron with meals may reduce gastrointestinal discomfort, though this may slightly decrease absorption 2, 6
• Starting with a lower dose and gradually increasing to the target dose may help reduce side effects 2
• If side effects persist despite adjustments, consider alternate-day dosing 1, 5

Special Considerations

• Intravenous iron should be considered if:
  • Oral iron is not tolerated despite adjustments 1
  • Ferritin levels do not improve with a trial of oral iron 1
  • The patient has a condition affecting absorption (e.g., inflammatory bowel disease, post-bariatric surgery) 1
• Iron supplements should not be taken within two hours of certain antibiotics due to interference with absorption 6

Monitoring Response

• In anemic patients, hemoglobin levels should increase by 1 g/dL within 2 weeks of supplementation 1
• Iron therapy should be continued for three months after correction of anemia to replenish iron stores 1
• If hemoglobin and iron indices don't improve despite adherence, consider switching to intravenous iron 1

Common Pitfalls to Avoid

• Taking iron more than once daily increases side effects without improving absorption due to hepcidin elevation 1, 2
• Discontinuing therapy prematurely before iron stores are fully replenished 1, 2
• Assuming all gastrointestinal symptoms are due to iron; persistent symptoms warrant medical evaluation 2
• Exceeding recommended dosage, which can lead to serious adverse effects 6