Would you recommend an iron infusion for a patient with mild iron deficiency, as indicated by low iron saturation and elevated TIBC?

Iron Infusion Decision for Mild Iron Deficiency

I would recommend oral iron supplementation first rather than proceeding directly to IV iron infusion for these laboratory values. Your patient has functional iron deficiency (low TSAT of 18% with adequate ferritin of 89 ng/mL), but does not meet the typical threshold criteria that would mandate IV iron as first-line therapy in most clinical contexts 1.

Key Laboratory Interpretation

Your patient's iron parameters indicate:

• TSAT 18% indicates functional iron deficiency (below the 20% threshold used across multiple guidelines) 1
• Ferritin 89 ng/mL is adequate and does not suggest absolute iron deficiency (above the typical 50-100 ng/mL thresholds) 1
• TIBC 250 mg/dL is at the lower end of normal, which actually argues against severe iron deficiency 1
• This pattern suggests functional iron deficiency rather than absolute iron deficiency 1

Clinical Context Matters

The appropriate route of iron supplementation depends critically on the underlying condition:

For General Iron Deficiency (Non-CKD, Non-Cancer)

• Start with oral iron 100-200 mg elemental iron daily 1
• Reserve IV iron for patients who fail oral therapy, cannot tolerate oral iron, or require rapid repletion 1, 2
• Your patient's ferritin of 89 ng/mL does not meet the typical threshold (<50 ng/mL) that would favor immediate IV therapy 1

For Chronic Kidney Disease on Hemodialysis

• IV iron would be appropriate if the patient is on hemodialysis with TSAT <20% and ferritin <100 ng/mL 1
• Target TSAT ≥20% and ferritin ≥100 ng/mL in this population 1
• Most hemodialysis patients require regular IV iron (25-125 mg weekly) to maintain targets 1

For Cancer-Related Anemia

• IV iron can be considered if TSAT <20% and ferritin between 30-800 ng/mL, particularly when used with erythropoiesis-stimulating agents (ESAs) 1
• Without ESA therapy, evidence for IV iron monotherapy is limited 1

For Heart Failure with Iron Deficiency

• IV iron is indicated for NYHA class II/III heart failure patients with ferritin <100 ng/mL or ferritin 100-300 ng/mL with TSAT <20% 3
• This is one context where IV iron has shown mortality benefit 1

Recommended Approach

Step 1: Assess the Clinical Context

• Determine if the patient has CKD on dialysis, cancer with chemotherapy, heart failure, or general iron deficiency 1
• Evaluate for ongoing blood loss or malabsorption that would favor IV therapy 1

Step 2: Initial Therapy Selection

• For most patients without the above conditions: Trial oral iron 100-200 mg elemental iron daily 1
• Consider alternate-day dosing to improve absorption and reduce side effects 1
• For hemodialysis patients: Proceed directly to IV iron (100-125 mg weekly for 8-10 doses) 1
• For heart failure patients: Use IV iron per protocol (see dosing below) 3

Step 3: Reassess in 4-8 Weeks

• Check CBC and iron parameters (ferritin, TSAT) 4-8 weeks after starting therapy 1
• Hemoglobin should increase by 1-2 g/dL if therapy is effective 1

Step 4: Consider IV Iron if Oral Fails

• If oral iron is not tolerated or ineffective after 4-8 weeks, transition to IV iron 1
• Modern IV iron formulations (ferric carboxymaltose, iron derisomaltose) allow total dose infusion of 1000-1500 mg 1, 3, 2

IV Iron Dosing (If Indicated)

If you proceed to IV iron based on clinical context:

• Ferric carboxymaltose: 750 mg IV × 2 doses separated by ≥7 days (for patients ≥50 kg) 3
• Iron derisomaltose: Up to 1000-1500 mg as single total dose infusion 1
• Iron sucrose: 100 mg weekly (requires multiple doses) 1

Important Safety Considerations

• Monitor serum phosphate with repeat IV iron courses, especially with ferric carboxymaltose, which can cause severe hypophosphatemia in 50-74% of patients 2
• Infusion reactions occur in <1% of patients with modern formulations 1, 2
• Avoid IV iron if ferritin >800 ng/mL and TSAT >50% as further benefit is unlikely and risk increases 1
• Check iron parameters 4-8 weeks after IV iron, not sooner, as circulating iron interferes with assays 1

Common Pitfall to Avoid

Do not assume that a "normal" ferritin (89 ng/mL) with low TSAT automatically requires IV iron 1. The ferritin is an acute phase reactant and can be falsely elevated in inflammation, but your patient's TIBC of 250 mg/dL (not elevated) suggests this is not primarily inflammatory 1. In the absence of specific indications (dialysis, heart failure, failed oral therapy), oral iron remains first-line 1.