What is the recommended dose of iron supplements for treating iron deficiency anemia?

Recommended Dose of Iron Supplements for Iron Deficiency Anemia

Start with 50-100 mg of elemental iron once daily, taken as a single morning dose on an empty stomach, using ferrous sulfate, ferrous fumarate, or ferrous gluconate. 1

Initial Dosing Strategy

• Begin with one tablet daily (e.g., ferrous sulfate 200 mg = 65 mg elemental iron) taken in the fasting state 1
• This lower dose approach (50-100 mg elemental iron) represents the optimal balance between efficacy and tolerability based on recent absorption studies 1
• Higher doses (≥60 mg elemental iron) stimulate hepcidin production, which paradoxically reduces iron absorption by 35-45% over the subsequent 24 hours 1

Alternative Dosing for Intolerance

If the patient cannot tolerate daily dosing:

• Switch to alternate-day dosing with the same or double dose (60-120 mg elemental iron every other day) 1
• Alternate-day administration significantly increases fractional iron absorption compared to daily dosing and reduces gastrointestinal side effects 1, 2
• The hepcidin elevation from iron doses subsides by 48 hours, making alternate-day dosing physiologically superior 2

Specific Populations

Pregnant women:

• Start with 30 mg elemental iron daily for prophylaxis at first prenatal visit 1
• Increase to 60-120 mg daily for treatment of confirmed iron deficiency anemia 1

Adolescent girls and non-pregnant women of childbearing age:

• Use 60-120 mg elemental iron daily for treatment 1

General adults with moderate anemia:

• 50-100 mg elemental iron once daily 1
• Typical oral iron supplement doses range from 100-200 mg daily in divided doses, though recent evidence favors lower single doses 1

Monitoring and Duration

• Check hemoglobin response at 2 weeks: A rise of <1.0 g/dL predicts treatment failure with 90% sensitivity and 79% specificity 1, 3
• If inadequate response at 2 weeks despite compliance, consider switching to parenteral iron 1, 3
• Monitor hemoglobin every 4 weeks until normalization 1
• Continue treatment for 3 months after hemoglobin normalizes to replenish iron stores 1

Critical Pitfalls to Avoid

Do not use twice-daily or three-times-daily dosing: Multiple daily doses do not increase total iron absorption compared to single daily doses, but significantly increase side effects 1

Do not switch between different ferrous salts for intolerance: This practice lacks evidence support 1. Instead, try alternate-day dosing, ferric maltol, or parenteral iron 1

Do not give afternoon or evening doses after a morning dose: The circadian increase in hepcidin is augmented by morning iron, reducing absorption from subsequent same-day doses 2

Do not use modified-release preparations as first-line: These are less suitable for prescribing due to reduced bioavailability 1

When to Consider Parenteral Iron

Switch to intravenous iron when: 1

• Oral iron is not tolerated despite alternate-day dosing
• No hemoglobin response after 4 weeks of compliant oral therapy
• Malabsorption syndromes present
• Ongoing blood loss exceeds oral replacement capacity
• Inflammatory bowel disease or chronic kidney disease present 1

The most studied intravenous formulation is ferric carboxymaltose, which can be infused over 15 minutes with maximum single doses up to 1000 mg 1