What is the recommended treatment for an adult patient, including premenopausal women, with iron deficiency, considering potential gastrointestinal disorders, kidney disease (Impaired renal function), and pregnancy?

Iron Deficiency Treatment in Adults

Start with oral ferrous sulfate 200 mg (65 mg elemental iron) once daily on an empty stomach as first-line therapy for iron deficiency in adults, including premenopausal women. 1

Initial Oral Iron Therapy

Recommended first-line regimen:

• Ferrous sulfate 200 mg once daily (providing 50-100 mg elemental iron) is the optimal starting dose 1
• Take on an empty stomach to maximize absorption 1
• Alternative ferrous salts (ferrous fumarate, ferrous gluconate) are equally effective if ferrous sulfate is unavailable 1

If gastrointestinal side effects occur:

• Switch to alternate-day dosing (one tablet every other day) rather than changing to a different ferrous salt, as this increases fractional iron absorption and reduces nausea 1
• Consider ferric maltol 30 mg twice daily if traditional iron salts are not tolerated, though this is more expensive and loads iron more slowly 1
• Do not switch between different traditional ferrous salts - this practice is not supported by evidence 1

Monitoring and Duration

Early monitoring protocol:

• Check hemoglobin at 4 weeks - expect a rise of at least 10 g/L (1 g/dL) 1
• Failure to achieve this rise indicates non-compliance, malabsorption, ongoing blood loss, or misdiagnosis 1

Treatment duration:

• Continue oral iron for approximately 3 months after hemoglobin normalizes to replenish iron stores 1
• Monitor blood counts every 6 months initially after treatment completion to detect recurrence 1

Special Population Considerations

Premenopausal women:

• Same treatment approach as general population 1
• Menstrual loss is the most common cause; investigate if age >45 years or if symptoms suggest GI pathology 1

Pregnancy:

• Oral iron remains first-line in first trimester 1
• Intravenous iron is preferred in second and third trimesters due to higher efficacy and lower GI side effects (relative risk 0.56 for GI adverse events) 1, 2

Gastrointestinal disorders:

• Celiac disease: Ensure gluten-free diet adherence first, then oral iron; use IV iron if stores don't improve 1
• Inflammatory bowel disease: Parenteral iron is more effective than oral therapy in active or chronic disease 1
• Post-bariatric surgery or malabsorption: Consider IV iron as first-line 1, 2

Chronic kidney disease (impaired renal function):

• Intravenous iron is indicated for hemodialysis patients receiving erythropoietin therapy 3
• Adult dose: 125 mg elemental iron IV per dialysis session, typically 1000 mg cumulative over 8 sessions 3
• Pediatric dose (≥6 years): 1.5 mg/kg (maximum 125 mg) IV per dialysis session 3

When to Use Intravenous Iron

Parenteral iron should be considered when: 1

• Oral iron is contraindicated, ineffective, or not tolerated
• Hemoglobin fails to rise ≥10 g/L after 2 weeks of daily oral therapy 1
• Chronic inflammatory conditions present (CKD, heart failure, IBD, cancer) 1, 2
• Ongoing blood loss exceeds oral replacement capacity 1
• Malabsorption syndromes (celiac disease, post-gastric surgery) 1, 2
• Second or third trimester pregnancy 1, 2

Available IV formulations: 1

• Ferric carboxymaltose: 1000 mg maximum single dose, 15-minute infusion, no test dose required
• Ferric derisomaltose: 20 mg/kg maximum single dose, 15-30 minute infusion, no test dose required
• Iron sucrose: 200 mg per injection, 30-minute infusion, test dose required
• Ferric gluconate (for hemodialysis): 125 mg per session 3

Critical safety consideration:

• Administer IV iron only where personnel and equipment for anaphylaxis treatment are immediately available 3
• Monitor for hypersensitivity reactions during and for at least 30 minutes after infusion 3

Common Pitfalls to Avoid

• Do not defer iron replacement while awaiting diagnostic investigations unless colonoscopy is imminent 1
• Do not prescribe modified-release oral iron preparations - they are less suitable and not evidence-based 1
• Do not use blood transfusion for routine iron deficiency anemia - reserve for severe symptomatic anemia or circulatory compromise (target Hb 70-90 g/L) 1
• Do not exceed 125 mg per dose of IV ferric gluconate - higher doses associated with increased adverse events 3
• Monitor phosphate levels with IV iron, especially ferric carboxymaltose, due to hypophosphatemia risk 4