What iron preparation and dosage do you recommend for a patient with a recent upper Gastrointestinal (GI) bleed?

Iron Replacement After Upper GI Bleed

For patients with iron deficiency anemia following an upper GI bleed, intravenous ferric carboxymaltose 1000-1500 mg administered as a single total dose infusion over 15 minutes is the optimal treatment, providing faster hemoglobin recovery, better tolerability, and superior iron repletion compared to oral iron. 1, 2

Why Intravenous Iron is Preferred

Intravenous iron should be the first-line treatment for post-GI bleed anemia rather than oral iron. The rationale is compelling:

• Faster hemoglobin recovery: IV ferric carboxymaltose achieves mean hemoglobin of 12.7 g/dL at 55 days post-discharge versus slower recovery with oral iron 2
• Superior efficacy: 60.4% of patients achieve ≥1 g/dL hemoglobin increase with IV iron versus only 34.7% with oral iron 3
• Better tolerability: Treatment-related adverse events occur in only 2.7% with IV iron versus 26.2% with oral iron 3
• Single-visit convenience: Complete iron repletion in one 15-minute infusion eliminates need for 4-7 visits required with older formulations 1

Specific IV Iron Formulation and Dosing

Ferric carboxymaltose (FCM) is the preferred formulation for post-GI bleed patients:

For patients ≥50 kg:

• 1500 mg total cumulative dose is optimal, as the average calculated iron deficit in IDA patients is 1531 mg 4
• Administer as 750 mg IV on day 1, then 750 mg IV at least 7 days later 5
• Alternative single-dose option: 1000 mg IV as a single infusion over 15 minutes 5

For patients <50 kg:

• 15 mg/kg body weight IV in two doses separated by at least 7 days 5

Administration details:

• Dilute up to 1000 mg in no more than 250 mL sterile 0.9% sodium chloride (minimum concentration 2 mg iron/mL) 5
• Infuse over at least 15 minutes 5
• For 1000 mg single dose, can administer as slow IV push over 15 minutes 5

Alternative IV Iron Formulations

If ferric carboxymaltose is unavailable, ferric derisomaltose (FDI) is an excellent alternative:

• Allows total dose infusion up to 20 mg/kg in a single administration 6
• Lower hypophosphatemia rates (4%) compared to FCM (up to 58%) 6
• Administer over 15-30 minutes 1

Low molecular weight iron dextran is another option:

• 1000 mg in 250 mL normal saline over 1 hour after a 25 mg test dose 6

When Oral Iron Might Be Considered

Oral iron is reasonable only for mild anemia in highly selected patients who:

• Have hemoglobin >10 g/dL at discharge
• Are hemodynamically stable throughout hospitalization
• Have no ongoing bleeding
• Can tolerate oral medications without GI distress

If oral iron is used:

• Ferrous sulfate 200 mg once daily (65 mg elemental iron) taken on empty stomach 1, 7
• Continue for 2-3 months after hemoglobin normalizes to replete iron stores 1
• Monitor hemoglobin at 2 weeks: failure to increase ≥10 g/L predicts treatment failure (90% sensitivity) 1

Monitoring After IV Iron

Check complete blood count and iron parameters 4-8 weeks after infusion 6:

• Expect hemoglobin increase of 1-2 g/dL within 4-8 weeks 6
• Target ferritin ≥50 ng/mL 1, 6
• In the post-GI bleed study, 94% of IV iron-treated patients achieved ≥2 g/dL hemoglobin increase by 4 months 8

Critical Pitfalls to Avoid

Iron deficiency after GI bleeding is severely undertreated: In one study, iron studies were ordered in only 50% of post-GI bleed patients, and when iron deficiency was diagnosed, only 7.1% received IV iron and 26.7% received oral iron 8

Do not use iron sucrose or ferric gluconate in outpatient settings: These formulations release more labile free iron, cause unacceptable reactions at doses >200-250 mg, and require 4-7 visits for complete repletion 1

Monitor for hypophosphatemia with FCM: Check serum phosphate in patients requiring repeat treatment within 3 months, as FCM has significantly higher hypophosphatemia rates than ferric derisomaltose 1, 6, 5

Avoid extravasation: Monitor IV site carefully as brown discoloration from extravasation may be long-lasting 5

Special Considerations for Upper GI Bleed Patients

Patients with upper GI bleeding often have impaired iron absorption due to:

• Gastric pathology (ulcers, gastritis)
• Proton pump inhibitor use (reduces iron absorption)
• Ongoing microscopic bleeding

This makes IV iron physiologically superior to oral iron in this population, as it bypasses the compromised GI absorption 6, 7

Blood transfusion alone is insufficient: Each unit of packed red cells contains only ~200 mg elemental iron, which does not replete the iron store deficit in severe IDA 1