What is the recommended dose of ferrous sulfate (iron supplement) for infants?

Ferrous Sulfate Dosing for Infants

Treatment Dose for Iron Deficiency Anemia

For infants with iron deficiency anemia, administer ferrous sulfate at 3 mg/kg per day of elemental iron, given between meals to maximize absorption. 1, 2, 3

Dosing Algorithm

• Standard therapeutic dose: 3 mg/kg/day of elemental iron 1, 2, 3, 4
• Administration timing: Between meals (not with food) to optimize absorption, as food can reduce iron bioavailability by up to 50% 2, 5
• Frequency: Can be given as a single daily dose or divided doses—both regimens show similar efficacy 6
• Duration: Continue for 4 weeks initially, then reassess 2, 3

Treatment Response Monitoring

• Confirm diagnosis: Hemoglobin should increase by ≥1 g/dL (or hematocrit by ≥3%) after 4 weeks of treatment 1, 2, 3
• Continue therapy: If response is adequate, continue for 2-3 additional months after correction to replenish iron stores 1, 2, 3
• Recheck: Monitor hemoglobin at end of treatment and again 6 months later 3

Preventive Supplementation Doses

For infants requiring iron supplementation for prevention (not treatment of anemia):

Term Infants

• Exclusively breastfed: 1 mg/kg/day starting at 6 months if insufficient iron from complementary foods 5
• Formula-fed: Use iron-fortified formula (no additional supplementation needed) 5

Preterm/Low Birthweight Infants

• Dose: 2-4 mg/kg/day (maximum 15 mg/day) 5
• Start: At 1 month of age 5
• Duration: Continue until 12 months of age 5

Critical Implementation Points

Formulation Selection

• Ferrous sulfate is superior to iron polysaccharide complex, resulting in 1.0 g/dL greater hemoglobin increase at 12 weeks and higher rates of complete IDA resolution (29% vs 6%) 4
• Use ionic iron salts (ferrous sulfate, fumarate, or gluconate) as they are most cost-effective and provide known amounts of elemental iron 5

Common Pitfalls to Avoid

• Do not give with meals or milk: Food reduces absorption by up to 50%; cow's milk should be limited to <24 oz/day in children 1-5 years 5
• Do not co-administer with aluminum-based phosphate binders: These reduce iron absorption 5
• Do not assume ascorbic acid helps: It does not improve ferrous iron absorption 5
• Do not discontinue for mild GI symptoms: Nausea, vomiting, and diarrhea are common but should not prompt discontinuation unless severe 2

When Treatment Fails

• If no response after 4 weeks despite compliance and absence of acute illness, obtain further laboratory evaluation (MCV, RDW, serum ferritin) to identify alternative causes 2
• Consider non-compliance, ongoing blood loss, malabsorption, or alternative diagnoses 3

Toxicity Concerns

• Avoid excessive dosing: Systemic iron toxicity with hepatocellular damage has been reported at 16 mg/kg 1, 2
• Monitor for iron overload in patients requiring repeated or prolonged courses 1