What is the recommended dose of intravenous (IV) iron?

Recommended Intravenous Iron Dosing

The standard recommended dose of intravenous iron is 1000 mg as a total dose infusion, though formulation-specific dosing varies: ferric carboxymaltose (FCM) is typically given as 750 mg twice (1500 mg total in the US) or 1000 mg single dose (outside US), ferric derisomaltose (FDI) allows 1000-1500 mg as a single infusion, and iron sucrose requires 200 mg doses repeated multiple times to reach 1000 mg total. 1

Formulation-Specific Dosing

Ferric Carboxymaltose (FCM)

• In the United States: 750 mg administered twice, separated by at least 7 days, for a total of 1500 mg per course 2
• Outside the United States: 1000 mg as a single infusion is standard practice 1
• Alternative single-dose regimen: 15 mg/kg body weight up to a maximum of 1000 mg may be given as a single dose 2
• For patients <50 kg: 15 mg/kg given in two doses separated by at least 7 days 2
• FCM should be diluted in 100 mL normal saline and infused over 20-30 minutes, or given as undiluted slow IV push over 15 minutes for 1000 mg doses 1, 2
• Important caveat: FCM causes treatment-emergent hypophosphatemia and should be avoided in patients requiring repeat infusions 1

Ferric Derisomaltose (FDI)

• Standard dose: 1000 mg as a single infusion 1
• Weight-based dosing: Up to 20 mg/kg, not to exceed 1500 mg 1
• FDI is the only formulation with FDA approval for total dose infusion 1
• Should be diluted in 100 mL normal saline 1
• Clinical advantage: FDI was the first IV iron formulation to demonstrate statistically significant reduction in cardiovascular death in heart failure patients 1

Iron Sucrose

• Standard dose: 200 mg per administration, given as IV push over 10 minutes without dilution 3
• Total requirement: Multiple doses needed to reach 1000 mg total 1, 3
• Frequency: Doses given every 2-3 weeks until total iron deficit is corrected 4
• Maximum single dose: Individual doses above 300 mg are not recommended 4
• No test dose required 3, 4

Iron Dextran (Low Molecular Weight)

• Test dose required: 25 mg slow IV push, wait 1 hour before main dose 4
• Standard dose: 100 mg IV over 5 minutes 4
• Regimen options: Weekly dosing for 10 doses (total 1000 mg) OR total dose infusion over several hours 4
• For CKD/dialysis patients: 500-1000 mg diluted in 250 mL normal saline infused over 1 hour 5, 4

Ferric Gluconate

• Test dose: 25 mg (strongly recommended for patients with previous sensitivities) 4
• Standard dose: 125 mg IV over 60 minutes 4
• Frequency: Once weekly for 8 doses (total 1000 mg) 4
• Individual doses above 125 mg are not recommended 4

Evidence Supporting 1000-1500 mg Total Dose

Why 1000 mg May Be Insufficient

• Calculated iron deficit: Studies using the modified Ganzoni formula show average iron deficits of 1392-1531 mg in patients with iron deficiency anemia 6
• Retreatment data: Patients receiving 1500 mg FCM had significantly lower retreatment rates (5.6%) compared to those receiving 1000 mg iron sucrose (11.1%, p<0.001) between days 56-90 6
• Clinical context: In inflammatory bowel disease, total doses up to 3600 mg may be required 7

Guideline-Supported Total Doses

• Cancer patients: Total doses in the range of 1000 mg significantly improved hematological response and quality of life 1
• General iron deficiency: 1000 mg total dose infusion is effective across multiple conditions including CKD, pregnancy, heavy uterine bleeding, inflammatory bowel disease, and heart failure 1

Special Population Dosing

Chronic Kidney Disease (Hemodialysis)

• Maintenance dosing: 100 mg per dialysis session, typically 3 times weekly 5, 3
• Initial repletion: 100-125 mg weekly for 8-10 doses when TSAT <20% and/or ferritin <100 ng/mL 5
• Administration method: Given as IV "push" over 2 minutes to minimize arthralgias/myalgias 5

Pediatric Patients

• Hemodialysis dosing: Weight <10 kg: 25 mg per dose; 10-20 kg: 50 mg per dose; >20 kg: 100 mg per dose 5, 4
• Predialysis/peritoneal dialysis: Weight <10 kg: 125 mg in 75 mL saline; 10-20 kg: 250 mg in 125 mL saline; >20 kg: 500 mg in 250 mL saline 5, 4

Heart Failure Patients (Iron Deficiency)

• Dosing based on weight and hemoglobin: For patients <70 kg with Hb <10 g/dL: 1000 mg on Day 1, then 500 mg at Week 6 2
• For patients ≥70 kg: 1000 mg on Day 1, then 1000 mg at Week 6 if Hb <10 g/dL 2
• Maintenance: 500 mg at 12,24, and 36 weeks if ferritin <100 ng/mL or ferritin 100-300 ng/mL with TSAT <20% 2

Frequency and Monitoring Considerations

When to Repeat Dosing

• Single cause eliminated: One total dose infusion should suffice 1
• Ongoing losses: Multiple administrations necessary for heavy menstrual bleeding, angiodysplasia, inflammatory bowel disease 1
• Malabsorption conditions: Repeat dosing needed for post-bariatric surgery, autoimmune gastritis, celiac disease 1

Laboratory Monitoring Timing

• After 100-125 mg weekly doses: Iron parameters can be measured without interrupting therapy 5
• After 200-500 mg doses: Wait at least 7 days before measuring iron parameters 5, 3
• After 1000 mg or larger doses: Wait at least 2-4 weeks before accurate assessment 1, 5
• Expected response: Hemoglobin should increase by 1-2 g/dL within 4-8 weeks 1

Target Iron Parameters

• Goal ferritin: 50 ng/mL in absence of inflammation 1
• In inflammatory conditions: Ferritin target of 100 ng/mL 1
• TSAT target: ≥20% 5

Critical Safety Considerations

Contraindications and Precautions

• Active infection: Do not administer IV iron during active bacteremia or infection 1, 4
• Iron overload: Avoid when TSAT >50% and/or ferritin >800 ng/mL 5
• Cardiotoxic chemotherapy: Avoid concomitant administration; give IV iron before, after, or at end of treatment cycle 1

Monitoring Requirements

• Observation period: Patients must be observed for at least 30 minutes post-infusion 1, 5
• Hypophosphatemia risk: Check serum phosphate levels in patients requiring repeat courses, especially with FCM 1, 2, 8
• Emergency preparedness: Resuscitation facilities must be immediately available, with staff trained to manage hypersensitivity reactions 1, 5

Common Pitfalls to Avoid

• Measuring iron parameters too early: Circulating iron interferes with assays within 4 weeks of total dose infusion, leading to spurious results 1
• Inappropriate intervention for minor reactions: Complement activation-related pseudo-allergy (CARPA) reactions resolve without therapy; using vasopressors and H1 blockers converts minor reactions into significant adverse events 9
• Underestimating total iron needs: 1000 mg may be insufficient for complete repletion in many patients; 1500 mg is closer to actual deficit 6