What is the recommended starting dosage of elemental iron for a patient with iron deficiency, considering their medical history and demographic characteristics?

Starting Iron Pill Dosage for Iron Deficiency

For most adults with iron deficiency, start with 50-100 mg of elemental iron taken once daily in the morning on an empty stomach. 1

Recommended Starting Regimen

Standard First-Line Approach

• Ferrous sulfate 200 mg tablet (containing 65 mg elemental iron) taken once daily is the gold standard and most cost-effective option 1, 2
• Take as a single morning dose on an empty stomach to maximize absorption 1, 3
• Once-daily dosing is superior to multiple daily doses because iron doses ≥60 mg stimulate hepcidin elevation that persists for 24 hours and blocks subsequent iron absorption 1, 4

Alternative Ferrous Salt Formulations

If ferrous sulfate is not tolerated, consider these alternatives (though evidence does not support improved tolerability with switching):

• Ferrous fumarate 325 mg tablet = 106-108 mg elemental iron 5
• Ferrous gluconate 324 mg tablet = 35-38 mg elemental iron 5, 6

Dosing Strategy Based on Severity

Mild to Moderate Anemia (Hemoglobin 10-12 g/dL in women, 10-13 g/dL in men)

• 50-100 mg elemental iron once daily 1
• This lower range minimizes side effects while providing adequate iron for repletion 1

Severe or Symptomatic Anemia

• 100-120 mg elemental iron once daily 3, 7
• The higher dose accelerates hemoglobin recovery when rapid correction is needed 3

Special Population Considerations

Inflammatory Bowel Disease Patients

• Maximum 100 mg elemental iron per day, and only when disease is clinically inactive 8
• Avoid oral iron entirely during active disease due to risk of exacerbating inflammation 8

Adolescents

• 60-120 mg elemental iron once daily in the morning 3
• Use the higher end (100-120 mg) for severe or symptomatic anemia 3

Chronic Kidney Disease

• 200 mg elemental iron per day divided into 2-3 doses 5
• This population requires higher total daily doses due to impaired iron utilization 5

Strategies to Optimize Absorption and Tolerability

Enhancing Absorption

• Take with 250-500 mg vitamin C to enhance absorption by forming an iron chelate 1
• Avoid taking within 2 hours of tea, coffee, or calcium-containing foods/medications, which inhibit absorption 1, 5

Managing Side Effects

If standard daily dosing causes intolerable gastrointestinal symptoms:

• Switch to alternate-day dosing with 100-200 mg elemental iron 1, 4
• Alternate-day dosing actually increases fractional iron absorption compared to daily dosing because hepcidin levels return to baseline by 48 hours 1, 4
• While the rate of hemoglobin rise may be slower initially, total iron absorption is higher 1

Monitoring Response to Treatment

Early Assessment (2-4 Weeks)

• Expect hemoglobin to increase by at least 10 g/L (1 g/dL) within 2 weeks 1
• Failure to achieve this rise strongly predicts treatment failure (sensitivity 90.1%, specificity 79.3%) and warrants investigation for non-compliance, continued blood loss, malabsorption, or concurrent B12/folate deficiency 1

Duration of Treatment

• Continue treatment for approximately 3 months after hemoglobin normalizes to adequately replenish iron stores 1, 3
• Monitor blood counts every 6 months initially to detect recurrent iron deficiency 5

Common Pitfalls to Avoid

• Do not prescribe multiple daily doses (e.g., three times daily), as the second and third doses result in 35-45% reduction in absorption due to hepcidin elevation 1
• Do not use modified-release preparations, as they are less suitable for prescribing and deliver iron past the duodenum where absorption is optimal 1
• Do not rely on multivitamin preparations alone, which typically contain only 14-30 mg elemental iron—insufficient for treating iron deficiency anemia 1
• Do not switch between different ferrous salts expecting better tolerability, as this is not supported by evidence 1

When to Consider Intravenous Iron

Switch to parenteral iron therapy when:

• Oral iron is not tolerated despite dosing modifications 1
• No improvement in ferritin levels after 4 weeks of adequate oral therapy 1
• Patient has conditions impairing oral iron absorption (inflammatory bowel disease, post-bariatric surgery, chronic kidney disease) 1
• Rapid correction is needed (e.g., pre-operative optimization, severe symptomatic anemia) 2

Modern IV iron formulations like ferric carboxymaltose or ferric derisomaltose can deliver 500-1000 mg in a single infusion and produce clinically meaningful hemoglobin response within one week 1, 2