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

Iron Dosing for Iron Deficiency Anemia

For adults with iron deficiency anemia, prescribe 60-120 mg of elemental iron daily, taken as a single morning dose on alternate days to maximize absorption and minimize side effects.

Age-Specific Dosing Recommendations

Infants and Young Children

• Infants and toddlers: 3 mg/kg per day of elemental iron, administered between meals 1
• Recheck hemoglobin after 4 weeks; an increase ≥1 g/dL confirms diagnosis 1
• Continue treatment for 2 additional months after hemoglobin normalizes 1

School-Age Children (5-12 years)

• One 60-mg iron tablet daily 1
• Combine with dietary counseling about iron-rich foods 1

Adolescent Boys (12-18 years)

• Two 60-mg iron tablets daily (total 120 mg) 1

Adolescent Girls and Nonpregnant Women (12-49 years)

• 60-120 mg elemental iron daily for treatment of anemia 1
• The dose can be adjusted within this range based on severity and tolerance 1

Pregnant Women

Prevention dosing:

• 30 mg elemental iron daily starting at first prenatal visit for routine supplementation 1

Treatment dosing for anemia:

• 60-120 mg elemental iron daily when anemia is diagnosed 1, 2
• Higher doses (60-100 mg daily) are prescribed for populations at increased risk 1
• Continue throughout pregnancy and 2-3 months postpartum 1, 2

Optimal Dosing Strategy Based on Recent Evidence

The alternate-day dosing approach is superior to traditional daily divided doses:

• Single doses ≥60 mg stimulate hepcidin elevation that persists 24 hours, blocking iron absorption from subsequent doses 3
• Give doses in the morning only, as afternoon/evening doses after a morning dose face increased hepcidin blocking absorption 3
• Alternate-day dosing (every 48 hours) maximizes fractional iron absorption since hepcidin subsides by 48 hours 3
• For faster hemoglobin response when needed, give twice the target daily dose on alternate days (e.g., 120 mg every other day instead of 60 mg daily) 3

Practical Implementation

Standard formulations available:

• Ferrous sulfate 324 mg tablets contain 65 mg elemental iron 4
• Ferrous gluconate 324 mg tablets contain 38 mg elemental iron 5
• Calculate total tablets needed based on elemental iron content 5, 4

Administration tips:

• Take iron between meals for optimal absorption 1
• Avoid taking with calcium supplements or antacids, which decrease absorption 6
• Consider taking with ascorbic acid (vitamin C) to enhance absorption 3
• Do not crush or chew tablets 5

Monitoring and Duration

Follow-up schedule:

• Recheck hemoglobin/hematocrit after 4 weeks of treatment 1, 2
• Expected response: hemoglobin increase ≥1 g/dL or hematocrit increase ≥3% 1
• Continue treatment for 2-3 months after hemoglobin normalizes to replenish iron stores 1, 7, 8
• Total treatment duration typically 3-6 months for complete store repletion 8

If no response after 4 weeks despite compliance:

• Evaluate with additional tests: MCV, RDW, serum ferritin 1
• Ferritin <15 μg/L confirms iron deficiency; >15 μg/L suggests alternative diagnosis 1
• Consider thalassemia minor or sickle cell trait in African, Mediterranean, or Southeast Asian ancestry 1
• Rule out malabsorption (celiac disease, atrophic gastritis, inflammatory bowel disease) 8

Special Populations and Adjustments

Vegetarian patients:

• May require almost twice the iron dose due to poor absorption of non-heme iron from plant sources 1, 6
• Consider prescribing at the higher end of the dosing range (100-120 mg daily) 6

Patients with gastrointestinal side effects:

• Reduce to lower end of dosing range (60 mg daily) or split the dose 8
• Consider alternate-day dosing, which reduces side effects while maintaining efficacy 9, 3
• Extended-release formulations may reduce gastrointestinal adverse effects 7

When to use intravenous iron:

• Oral therapy fails despite compliance 2
• Severe anemia requiring rapid correction 8, 9
• Intestinal malabsorption confirmed 8
• Specific conditions: dialysis-dependent renal insufficiency, heart failure, active inflammatory bowel disease 9

Common Pitfalls to Avoid

• Prescribing divided doses throughout the day: This increases hepcidin and blocks absorption from later doses 3
• Giving afternoon/evening doses: Circadian hepcidin elevation is augmented by morning iron, blocking later doses 3
• Stopping treatment when hemoglobin normalizes: Iron stores require 2-3 additional months to replenish 1, 7
• Failing to identify higher-risk patients: Women with heavy menstrual bleeding, vegetarians, and those with short pregnancy intervals need closer monitoring 1, 6
• Relying solely on hemoglobin: Check ferritin to assess iron stores, as hemoglobin can normalize while stores remain depleted 6