How should ferrous fumarate be dosed in healthy adults, children aged 2–12 years, and infants, and what are the contraindications and special precautions?

Ferrous Fumarate Dosing

For adults with iron deficiency anemia, prescribe ferrous fumarate 100-106 mg elemental iron once daily (one 305-322 mg tablet), taken between meals, as this provides optimal absorption with minimal side effects compared to higher or more frequent dosing. 1

Adult Dosing (Iron Deficiency Anemia)

Standard Treatment Regimen

• Initial dose: One tablet daily of ferrous fumarate 305-322 mg (providing 100-106 mg elemental iron) 1
• Timing: Take between meals on an empty stomach to maximize absorption 1
• Duration: Continue for approximately 3 months after hemoglobin normalization to replenish iron stores 1

Dosing Rationale

The once-daily regimen is based on evidence showing that 60 mg elemental iron stimulates hepcidin levels, reducing subsequent iron absorption by 35-45%. 1 Consequently, overall iron absorption from 60 mg once daily is similar to 60 mg twice daily, making higher frequency dosing unnecessary and potentially counterproductive. 1

Alternative Dosing for Intolerance

• If gastrointestinal side effects occur: Reduce to one tablet every other day (alternate-day dosing) 1
• Alternate-day administration significantly increases fractional iron absorption compared to daily dosing in iron-depleted individuals 1
• This approach maintains efficacy while improving tolerability 1, 2

Monitoring Protocol

• Week 2-4: Check hemoglobin; expect rise of ≥10 g/L after 2 weeks of daily therapy 1
• Absence of this response strongly predicts treatment failure (sensitivity 90.1%, specificity 79.3%) and warrants investigation for non-compliance, malabsorption, or alternative diagnoses 1
• After hemoglobin normalization: Continue treatment for 3 additional months to replenish iron stores 1

Pediatric Dosing

Infants and Young Children (Ages 6 months to <5 years)

• Treatment dose: 3 mg/kg/day of elemental iron, administered as ferrous sulfate drops between meals 1, 3
• Initial treatment period: 4 weeks 1, 3
• Response confirmation: Hemoglobin increase ≥1 g/dL (or hematocrit ≥3%) confirms iron deficiency anemia 1, 3
• Total duration: If confirmed, continue for 2 additional months (total ~3 months) 1, 3
• Follow-up: Recheck hemoglobin approximately 6 months after completing treatment 1, 3

Important caveat: While ferrous fumarate is available in liquid formulations (140 mg/5 mL providing 45 mg/5 mL elemental iron) 1, isotope studies show iron-deficient children absorb iron from ferrous fumarate only ~30% as well as from ferrous sulfate (relative bioavailability 30 vs. 100). 4 Therefore, ferrous sulfate drops remain the preferred formulation for treating iron deficiency anemia in infants and young children. 1, 3

School-Age Children (Ages 5 to <12 years)

• Treatment dose: One 60 mg elemental iron tablet daily 1
• Follow-up and laboratory evaluation identical to infants 1

Adolescent Boys (Ages 12 to <18 years)

• Treatment dose: Two 60 mg elemental iron tablets daily (120 mg total elemental iron) 1
• Follow-up and laboratory evaluation identical to younger children 1

Adolescent Girls (Ages 12 to <18 years)

• Treatment dose: 60-120 mg elemental iron daily 1
• This translates to one to two ferrous fumarate 305 mg tablets (100-200 mg elemental iron) daily 1

Available Ferrous Fumarate Formulations

Preparation	Total Dose	Elemental Iron	Cost per 28 days
Tablet	210 mg	69 mg	£1.33
Capsule	305 mg	100 mg	£1.40
Tablet	322 mg	106 mg	£1.00
Liquid	140 mg/5 mL	45 mg/5 mL	£4.00

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Contraindications and Precautions

Absolute Contraindications

• Hemoglobin >15 g/dL (do not administer iron) 1
• Hemochromatosis or other iron overload conditions 1
• Hypersensitivity to ferrous fumarate or any component 1

Special Precautions

• Pregnancy: Low-dose prophylactic ferrous fumarate (40 mg elemental iron daily) is not associated with clinically significant gastrointestinal complaints 5
• Renal insufficiency: Consider parenteral iron in dialysis-dependent patients, as it is more effective than oral supplementation 2
• Active inflammatory bowel disease: Parenteral iron is more effective than oral therapy 2
• Chronic heart failure: Parenteral iron may be preferred for functional iron deficiency 1, 2

Monitoring for Iron Overload

• Monitor serum ferritin levels during long-term therapy 1, 3
• Ferritin should preferably not exceed 500 μg/L to avoid toxicity, especially in children and adolescents 1

Common Pitfalls and How to Avoid Them

Pitfall 1: Excessive Dosing

Problem: Prescribing 200 mg elemental iron three times daily (traditional dosing) increases side effects without improving absorption. 1, 2
Solution: Use once-daily dosing of 50-100 mg elemental iron for adults. 1

Pitfall 2: Taking Iron With Meals

Problem: Food significantly reduces iron bioavailability. 1, 3
Solution: Instruct patients to take iron between meals on an empty stomach. 1, 3

Pitfall 3: Premature Discontinuation

Problem: Stopping treatment when hemoglobin normalizes leaves iron stores depleted. 1
Solution: Continue therapy for 3 months after hemoglobin normalization to replenish stores. 1

Pitfall 4: Using Ferrous Fumarate in Iron-Deficient Infants

Problem: Ferrous fumarate has only 30% relative bioavailability compared to ferrous sulfate in iron-deficient children. 4
Solution: Use ferrous sulfate drops (not fumarate) for treating iron deficiency anemia in infants and young children. 1, 3, 4

Pitfall 5: Failing to Monitor Early Response

Problem: Missing treatment failure or non-compliance. 1
Solution: Check hemoglobin at 2-4 weeks; absence of ≥10 g/L rise predicts failure and requires investigation. 1