How should intravenous iron be administered to an adult with iron‑deficiency anemia?

How to Administer Intravenous Iron

Intravenous iron should be given using formulations that allow complete iron repletion in 1–2 infusions, with ferric carboxymaltose (750–1000 mg over 15 minutes) or ferric derisomaltose (1000 mg single infusion) as preferred first-line agents, always in a facility equipped for emergency resuscitation. 1

Indications for IV Iron Over Oral Therapy

Before administering IV iron, confirm that the patient meets at least one of these criteria:

• Intolerance to ≥2 different oral iron formulations (ferrous sulfate, fumarate, or gluconate) 1
• Active inflammatory bowel disease with hemoglobin <10 g/dL, where inflammation-driven hepcidin blocks oral absorption 1
• Post-bariatric surgery patients, due to disrupted duodenal iron absorption 1
• Failure of ferritin to improve after 4 weeks of compliant oral therapy 1
• Celiac disease with inadequate response to oral iron despite strict gluten-free diet 1
• Ongoing GI blood loss exceeding oral replacement capacity 1
• Chronic heart failure with iron deficiency (ferritin <100 ng/mL or 100–300 ng/mL with transferrin saturation <20%) 1

Preferred IV Iron Formulations & Dosing

First-Line Agents

Ferric carboxymaltose:

• Dose: 750–1000 mg per infusion 1, 2
• Infusion time: 15 minutes 1
• Schedule: Two doses given ≥7 days apart provide total 1500 mg 1
• Dilution: Administer in 100–250 mL normal saline 1

Ferric derisomaltose:

• Dose: 1000 mg as a single infusion 1, 3
• Infusion time: 15–20 minutes 3
• Advantage: Complete repletion in one visit 3, 4

Alternative Agents (When First-Line Not Available)

Iron sucrose:

• Maximum dose: 200 mg per infusion 1
• Infusion time: 10 minutes for bolus dosing 1
• Limitation: Requires multiple visits to achieve repletion 1
• Dilution: Can be given undiluted as slow IV push or diluted in 100 mL normal saline 1

Iron gluconate:

• Maximum dose: 125 mg per infusion 1, 5
• Infusion time: 1 hour when diluted in 100 mL normal saline 5
• Adult dose: 10 mL (125 mg elemental iron) per dialysis session 5
• Pediatric dose (≥6 years): 0.12 mL/kg (1.5 mg/kg elemental iron) diluted in 25 mL normal saline over 1 hour 5

Low molecular weight iron dextran:

• Can deliver >1000 mg in single infusion 1
• NOT recommended as first-line due to higher anaphylaxis risk (0.6–0.7%) 1
• Requires test dose prior to full infusion 1

Step-by-Step Administration Protocol

Pre-Infusion Requirements

1. Verify resuscitation equipment is immediately available: epinephrine, antihistamines, corticosteroids, oxygen, airway management supplies 1
2. Obtain baseline vital signs (blood pressure, heart rate, respiratory rate) 1
3. Establish secure IV access with normal saline running 1
4. Do NOT mix IV iron with other medications or add to parenteral nutrition 5
5. Administer only in 0.9% sodium chloride, never dextrose solutions 5

During Infusion

1. Monitor patient continuously for first 15 minutes, then every 15 minutes until completion 1
2. Watch for signs of hypersensitivity: flushing, chest tightness, dyspnea, hypotension, urticaria 1
3. Most reactions are complement-activation pseudo-allergies (CARPA), not true anaphylaxis 1
4. If mild infusion reaction occurs: stop infusion, wait 15 minutes, restart at slower rate 1
5. If severe reaction: stop infusion immediately, administer epinephrine and supportive care 1

Post-Infusion Monitoring

1. Observe patient for ≥30 minutes after infusion completion and until clinically stable 1, 5
2. Monitor blood pressure for hypotension, which can occur during or after infusion 1, 5
3. Check phosphate levels 2–4 weeks post-infusion, especially with ferric carboxymaltose (risk of hypophosphatemia) 2, 6

Expected Hematologic Response

• Hemoglobin rise: Approximately 2 g/dL within 3–4 weeks 1
• Ferritin increase: Typically 400+ ng/mL within 4–6 weeks 1
• Recheck labs at 4 weeks: hemoglobin, ferritin, transferrin saturation 1

Special Population Considerations

Chronic Kidney Disease Patients

• Iron gluconate or iron sucrose are FDA-approved for CKD patients 1, 5
• Administer during dialysis sessions when possible 5
• Monitor for iron overload with regular ferritin checks 1

Inflammatory Bowel Disease

• IV iron is first-line when hemoglobin <10 g/dL with active inflammation 1
• Odds ratio 1.57 for achieving ≥2.0 g/dL hemoglobin increase vs. oral iron 1
• Better tolerated than oral iron in this population 1

Pregnancy

• Safe during second and third trimesters when oral iron fails 1
• Avoid formulations containing benzyl alcohol in premature/low-birth-weight infants 5
• Risk of hypersensitivity reaction may have serious fetal consequences 5

Pediatric Patients (≥6 years)

• Iron gluconate: 0.12 mL/kg (1.5 mg/kg elemental iron) over 1 hour 5
• Safety not established in children <6 years 5

Critical Safety Pitfalls to Avoid

• Do NOT use iron dextran as first-line due to higher anaphylaxis risk 1
• Do NOT administer IV iron to patients with iron overload (ferritin >500 ng/mL without inflammation) 1
• Do NOT give rapid infusion of ferumoxytol (original labeling revised after postmarketing reactions) 1
• Do NOT skip post-infusion monitoring; reactions can occur up to 30 minutes after completion 1, 5
• Do NOT forget to monitor phosphate levels with ferric carboxymaltose (risk of hypophosphatemia/osteomalacia) 2, 6
• Do NOT administer without resuscitation equipment immediately available 1

Contraindications

• Known hypersensitivity to the specific IV iron formulation or its components 5
• Evidence of iron overload (ferritin >500 ng/mL in absence of inflammation) 1
• Active infection or sepsis (relative contraindication; defer until infection controlled) 1

Advantages of IV Over Oral Iron

• Bypasses GI absorption barriers in malabsorption syndromes 1, 4
• Overcomes hepcidin-mediated blockade in inflammatory conditions 1
• Eliminates adherence concerns with single or two-dose regimens 3, 4
• Reduces healthcare resource utilization compared to multiple oral prescriptions 3
• Better tolerated in patients with GI side effects from oral iron 1, 7