What is the recommended iron supplementation protocol, including oral and intravenous dosing, duration, and monitoring?

Iron Supplementation Protocol

Start with oral ferrous sulfate once daily or every other day in the morning on an empty stomach with vitamin C, and switch to intravenous iron if oral therapy fails, is not tolerated, or absorption is impaired. 1

Oral Iron Supplementation

Formulation and Dosing

• Use ferrous sulfate as the preferred formulation due to lowest cost and equivalent efficacy to other oral iron preparations 1
• Dose once daily at most, with 60-120 mg elemental iron 2
• Every-other-day dosing is equally or more effective than daily dosing because oral iron doses ≥60 mg stimulate hepcidin elevation that persists 24 hours and blocks absorption of subsequent doses 1, 2
• Total treatment duration typically requires 3-12 weeks to correct anemia and replenish stores 3

Administration Technique

• Give in the morning on an empty stomach to maximize absorption, as circadian hepcidin increases are augmented by morning iron doses 4, 2
• Co-administer with approximately 100 mg vitamin C (as a tablet) or a glass of orange/citrus juice to enhance absorption 1, 4
• If vitamin C unavailable, dose with plain water 4
• Avoid afternoon or evening dosing after a morning dose due to hepcidin-mediated absorption blockade 2
• Take with a full glass of liquid and remain upright for 30-60 minutes to prevent pill esophagitis 4

What Impairs Absorption (Avoid These)

• Food, especially cereals and grains 4
• Beverages including milk, tea, and coffee 4
• Calcium supplements, antacids, H2 inhibitors, and proton pump inhibitors 4

Intravenous Iron Therapy

Indications for IV Iron

Switch to IV iron when: 1

• Patient does not tolerate oral iron
• Ferritin levels fail to improve after adequate trial of oral iron
• Conditions where oral absorption is impaired (post-bariatric surgery, celiac disease, autoimmune gastritis, inflammatory bowel disease with active inflammation)
• Rapid correction needed (e.g., pre-operative)

IV Formulation Selection

• Prefer formulations allowing 1-2 total infusions over those requiring multiple doses 1
• High-dose options include ferric carboxymaltose (500-1000 mg/infusion), ferric derisomaltose (up to 1500 mg or 20 mg/kg), and iron dextran (500-1000 mg) 1, 3, 5
• All IV iron formulations have similar safety profiles; true anaphylaxis is very rare (<1% moderate-severe reactions) 1
• Most reactions are complement activation-related pseudo-allergy (infusion reactions), not true anaphylaxis 1

IV Administration

• Dilute appropriately (e.g., ferric derisomaltose in 100 mL normal saline) 1
• Must administer in medical facilities with healthcare providers trained to manage hypersensitivity reactions 3
• Monitor serum phosphate levels, especially with ferric carboxymaltose, which causes hypophosphatemia in 50-74% of patients 5

Monitoring Protocol

Timing of Laboratory Assessment

• Check CBC and iron parameters 4-8 weeks after last infusion 1
• Do not check iron parameters within 4 weeks of IV iron as circulating iron interferes with assays, producing spurious results 1
• Hemoglobin should increase 1-2 g/dL within 4-8 weeks of therapy 1

Target Parameters

• Goal ferritin: ≥50 ng/mL in absence of inflammation 1
• Transferrin saturation (TSAT) >20% indicates adequate iron 1
• Keep ferritin <800-1000 ng/mL and TSAT <50% to avoid iron overload 6

Interpreting Discordant Results

• TSAT <20% has high sensitivity for iron deficiency (absolute or functional) 1
• Ferritin <100 ng/mL has low sensitivity (35-48%) in inflammatory states 1
• In inflammation with elevated ferritin but low TSAT, iron deficiency is still present 1
• Consider soluble transferrin receptor (sTfR) or reticulocyte hemoglobin content (CHr/RET-He) when ferritin is unreliable due to inflammation 1

Special Populations

Inflammatory Bowel Disease

• Determine if anemia is from inadequate intake/absorption versus GI bleeding 1
• Treat active inflammation to enhance absorption 1
• Use IV iron with active inflammation and compromised absorption 1

Post-Bariatric Surgery

• Use IV iron therapy due to disrupted duodenal absorption 1

Celiac Disease

• Ensure gluten-free diet adherence to improve absorption 1
• Try oral iron first based on severity and tolerance, then IV if stores don't improve 1

Common Pitfalls

• Dosing oral iron multiple times daily reduces absorption and increases side effects 1, 2
• Checking iron parameters too soon after IV iron yields false results 1
• Assuming elevated ferritin excludes iron deficiency in inflammatory conditions 1
• Not monitoring phosphate with ferric carboxymaltose, risking osteomalacia and fractures 5