What is the dose and duration of iron repletion therapy for a patient with iron deficiency anemia, given lab results showing elevated Iron Binding Capacity (Total Iron Binding Capacity), low percent saturation, and low ferritin levels?

Iron Repletion Therapy for Severe Iron Deficiency

Based on your labs showing severe iron deficiency (ferritin 8 ng/mL, transferrin saturation 13%), start oral ferrous sulfate 200 mg once daily (providing 65 mg elemental iron) taken on an empty stomach, and continue for 3 months after hemoglobin normalizes to fully replenish iron stores. 1, 2

Dosing Regimen

Oral Iron - First-Line Therapy:

• Ferrous sulfate 200 mg once daily is the optimal starting dose, providing 65 mg of elemental iron 1, 2
• Take in the fasting state (before meals) to maximize absorption 1
• If gastrointestinal side effects occur, switch to alternate-day dosing (ferrous sulfate 200 mg every other day) rather than discontinuing—this maintains reasonable efficacy with significantly fewer side effects 1
• Alternative: 60 mg elemental iron twice daily produces faster hemoglobin rise than alternate-day dosing, though with more GI symptoms 1
• Consider adding vitamin C 250-500 mg with each iron dose to enhance absorption 2

Alternative oral preparations (if ferrous sulfate not tolerated):

• Ferrous fumarate or ferrous gluconate are equally effective 2
• Ferric maltol is an option for significant GI intolerance 1

Duration of Treatment

Critical timing considerations:

• Continue oral iron for 2-3 months AFTER hemoglobin normalizes to replenish iron stores 1, 2
• With your ferritin of 8 ng/mL (severely depleted stores), expect to need 4-6 months total treatment duration 1
• Do not stop iron prematurely when hemoglobin normalizes—this is a common pitfall that leads to recurrent deficiency 2

Expected Response & Monitoring

Check hemoglobin at 2 weeks:

• Expect hemoglobin rise of at least 1 g/dL (10 g/L) after 2 weeks of daily oral therapy 2, 3
• Failure to achieve this indicates non-compliance, malabsorption, continued bleeding, or need for IV iron 2

Recheck at 4-8 weeks:

• Expect hemoglobin increase of 1-2 g/dL within 4-8 weeks 1
• Measure ferritin and transferrin saturation 4-8 weeks after starting therapy 1

Target iron parameters:

• Ferritin ≥50 ng/mL (in absence of inflammation) 1
• Transferrin saturation ≥20% 1

Monitor every 4 weeks until hemoglobin normalizes, then continue iron for additional 2-3 months 1

When to Switch to Intravenous Iron

Consider IV iron if:

• Intolerance to at least two different oral iron preparations 2
• No hemoglobin rise ≥1 g/dL after 2 weeks of adequate oral therapy 2
• Malabsorption conditions (celiac disease, inflammatory bowel disease, post-bariatric surgery) 2, 4
• Ongoing blood loss that cannot be controlled 1
• Severe symptomatic anemia requiring rapid correction 2

IV iron dosing options (if needed):

• Ferric carboxymaltose: 1000 mg single infusion over 15 minutes (can repeat once after 1 week if needed) 1, 5, 6
• Ferric derisomaltose: 1000 mg single infusion over 15-30 minutes 1
• Iron sucrose: 200 mg per injection over 30 minutes (multiple doses needed) 1

Common Pitfalls to Avoid

• Don't stop oral iron when hemoglobin normalizes—continue for 2-3 additional months to replenish stores 1, 2
• Don't use modified-release iron preparations—they have reduced absorption and are less effective 2
• Don't assume dietary deficiency alone—investigate for pathological blood loss, especially if age >45 years or male 2, 3
• Don't switch between different oral iron salts for intolerance—this is not evidence-based; instead try alternate-day dosing or consider IV iron 1
• Don't check iron parameters within 4 weeks of starting IV iron—circulating iron interferes with assays 1

Investigating the Underlying Cause

Your severely low ferritin (8 ng/mL) and low saturation (13%) require investigation for blood loss:

• If age >45 years or male: Upper endoscopy AND colonoscopy to exclude GI bleeding or malignancy 2, 3
• If age <45 years and female: Consider heavy menstrual bleeding, but still investigate if symptoms persist 2
• Screen for celiac disease (anti-endomysial antibodies with IgA level) 2
• Evaluate for other malabsorption conditions 2, 4