In a 71-year-old man with anemia and low ferritin, low serum iron, and low transferrin saturation, what iron therapy should be initiated?

Initial Treatment for Iron Deficiency Anemia in a 71-Year-Old Man

Start with oral ferrous sulfate 325 mg once daily (or on alternate days), taken on an empty stomach, as first-line therapy for this patient with clear iron deficiency anemia. 1, 2, 3

Diagnostic Confirmation

Your patient has absolute iron deficiency anemia based on:

• Ferritin 19 ng/mL (well below the diagnostic threshold of <45 ng/mL) 2
• Transferrin saturation 10% (significantly below the 20% threshold) 1, 2
• These values confirm true iron deficiency, not functional deficiency from inflammation 2

First-Line Treatment: Oral Iron

Initiate oral ferrous sulfate 325 mg once daily as the standard starting regimen 1, 2, 3:

• Dosing strategy: 50-100 mg elemental iron daily (ferrous sulfate 325 mg contains ~105 mg elemental iron) is the optimal compromise between efficacy and tolerability 1
• Timing: Take on an empty stomach for best absorption; if not tolerated, can take with meals (though absorption decreases) 2
• Frequency: Once daily dosing is sufficient—hepcidin remains elevated for 48 hours after iron intake, blocking further absorption with more frequent dosing 2
• Alternative regimen: Alternate-day dosing (every other day) may improve tolerance with similar ultimate efficacy, though this requires further study 1, 2

Absorption Enhancement

• Add vitamin C 500 mg with iron to improve absorption even if calcium or fiber present in meals 2
• Taking iron with meat protein further enhances absorption 2

Monitoring Response

Assess hemoglobin response at 2 weeks 1:

• Expected response: Hemoglobin should rise ≥10 g/L after 2 weeks of daily oral iron 1
• Failure to respond: Absence of ≥10 g/L rise has 90.1% sensitivity and 79.3% specificity for predicting subsequent treatment failure 1

When to Switch to Intravenous Iron

Consider IV iron if any of the following occur 2, 3, 4:

• Intolerance to oral iron (nausea, constipation, abdominal pain—occurs in 12%, 12%, and 11% respectively) 2
• Inadequate response at 2-4 weeks despite adherence 1, 4
• Malabsorption conditions identified during workup (celiac disease, atrophic gastritis, post-bariatric surgery) 3
• Ongoing blood loss that cannot be controlled 3
• Chronic inflammatory conditions if discovered (though less likely given his low ferritin) 2, 3

Critical Next Step: Investigate the Cause

In a 71-year-old man, bidirectional endoscopy (upper and lower GI) is mandatory to identify the source of iron deficiency 4:

• Recurrent blood loss accounts for 94% of iron deficiency cases 4
• Men and postmenopausal women require GI evaluation as standard practice 2, 4
• Test for Helicobacter pylori (noninvasive testing recommended as common cause) 2, 4
• Test for celiac disease (tissue transglutaminase antibody) 2, 4

Common Pitfalls to Avoid

• Do not prescribe iron more than once daily—this increases side effects without improving absorption due to hepcidin regulation 2
• Do not use modified-release preparations—these are less suitable for prescribing 1
• Do not switch between different oral iron salts (ferrous sulfate to ferrous gluconate) if side effects occur—no evidence supports this practice; instead consider alternate-day dosing or IV iron 1
• Do not delay GI investigation in elderly men—this population requires prompt evaluation for occult malignancy 4