In a 70‑year‑old female with mild anemia (hemoglobin 11.8 g/dL, hematocrit 35.2 %), serum iron 115 µg/dL, total iron‑binding capacity 398 µg/dL, transferrin saturation 29 %, ferritin 18 ng/mL, C‑reactive protein 15.6 mg/L, and normal thyroid‑stimulating hormone, what is the appropriate evaluation and treatment for her iron‑deficiency anemia?

Evaluation and Treatment of Iron Deficiency Anemia in a 70-Year-Old Woman

This patient has confirmed iron deficiency anemia (ferritin 18 ng/mL with hemoglobin 11.8 g/dL) complicated by inflammation (CRP 15.6 mg/L), and requires both oral iron supplementation and bidirectional endoscopy to identify the underlying cause of blood loss. 1

Diagnostic Interpretation

Iron Deficiency Confirmation

• Ferritin 18 ng/mL definitively confirms iron deficiency even in the presence of inflammation (CRP 15.6 mg/L), as this value falls well below the diagnostic threshold of <45 ng/mL for iron deficiency. 1
• The transferrin saturation of 29% is actually above the typical iron deficiency threshold (<20%), but this can occur in early or mixed iron deficiency states, particularly when inflammation is present. 2, 3
• In elderly patients, a ferritin ≤18 ng/mL has a likelihood ratio of 41.47 for iron deficiency, making the diagnosis virtually certain (>95% probability). 4

Inflammation Impact

• The elevated CRP (15.6 mg/L) indicates concurrent inflammation, which can mask the severity of iron deficiency by artificially elevating ferritin levels above what they would otherwise be. 2
• Despite inflammation, this patient's ferritin remains very low (18 ng/mL), suggesting true absolute iron deficiency rather than functional iron deficiency. 5

Mandatory Gastrointestinal Evaluation

Bidirectional endoscopy (both upper endoscopy and colonoscopy) is strongly recommended and should be performed at the same setting. 1

Rationale for Endoscopy

• The AGA provides a strong recommendation (moderate-quality evidence) for bidirectional endoscopy in all asymptomatic postmenopausal women with iron deficiency anemia. 1
• In patients over 65 years with iron deficiency anemia, 9% have gastrointestinal cancer when evaluated endoscopically. 6
• Recurrent blood loss accounts for 94% of iron deficiency anemia cases in this population. 3

Additional Non-Invasive Testing

• Test for Helicobacter pylori infection (urea breath test or stool antigen), as this is a common and treatable cause of iron deficiency anemia. 3
• Screen for celiac disease with tissue transglutaminase IgA antibody and total IgA level, as celiac disease causes malabsorption and is frequently missed. 2, 3

Iron Replacement Strategy

Oral Iron as First-Line Treatment

Start oral ferrous sulfate 325 mg (65 mg elemental iron) once daily on an empty stomach in the morning. 7, 2

Optimal Administration

• Take iron on an empty stomach (1 hour before or 2 hours after meals) to maximize absorption, as food can reduce absorption by up to 50%. 7
• Morning dosing is preferred because hepcidin levels are lowest in the morning and increase throughout the day. 7
• Add 500 mg vitamin C when taking iron to significantly enhance absorption, even if taken with meals. 7

What to Avoid

• Avoid coffee or tea within 1-2 hours of iron intake (coffee decreases absorption by 54%). 7
• Avoid calcium-containing foods or supplements at the time of iron administration. 7

Alternative Dosing for Intolerance

• If gastrointestinal side effects occur (nausea, constipation, abdominal discomfort), switch to alternate-day dosing (ferrous sulfate 325 mg every other day), which significantly increases fractional absorption while reducing symptoms. 7

Monitoring Response

Check hemoglobin at 4 weeks to assess response. 7, 3

• An increase of ≥1 g/dL (or ≥10 g/L) confirms adequate response to oral iron. 7, 6
• If hemoglobin rises appropriately, continue oral iron for 3 months total (including the initial 4 weeks) to adequately replenish iron stores. 7
• The absence of hemoglobin rise of at least 1 g/dL after 4 weeks strongly predicts treatment failure and necessitates switching to intravenous iron. 7

When to Use Intravenous Iron

Intravenous iron is NOT first-line for this patient because her hemoglobin is 11.8 g/dL (above the 10 g/dL threshold for severe anemia). 8

However, switch to intravenous iron if:

• No hemoglobin response after 4 weeks of documented adherence to oral iron. 2, 3
• Intolerable gastrointestinal side effects despite alternate-day dosing. 2
• Ongoing blood loss is identified on endoscopy that cannot be immediately controlled. 2
• Malabsorption is diagnosed (celiac disease, atrophic gastritis, prior bariatric surgery). 2

Common Pitfalls to Avoid

• Do not delay endoscopy while treating with iron—the evaluation for gastrointestinal malignancy should proceed concurrently with iron replacement. 1
• Do not use the ferritin threshold of <15 ng/mL to diagnose iron deficiency, as this has only 59% sensitivity and will miss 41% of cases; the threshold of <45 ng/mL has 85% sensitivity. 1
• Do not assume the elevated CRP invalidates the low ferritin—a ferritin of 18 ng/mL confirms iron deficiency even with inflammation present. 1, 2
• Do not use modified-release or enteric-coated iron preparations, as they release iron beyond the duodenum where absorption is limited. 7
• Do not continue oral iron indefinitely without monitoring—check response at 4 weeks to identify treatment failure early. 3