What is the appropriate evaluation and initial management for an adult male or post‑menopausal female with iron saturation 13 % and ferritin 23 ng/mL?

Evaluation and Management of Iron Deficiency in an Adult Male or Postmenopausal Female

This patient has confirmed absolute iron deficiency (ferritin 23 ng/mL, transferrin saturation 13%) and requires immediate oral iron supplementation plus urgent bidirectional endoscopy to exclude gastrointestinal malignancy. 1

Diagnostic Confirmation

Your laboratory values definitively confirm iron deficiency:

• Ferritin 23 ng/mL falls below the 30 μg/L threshold that indicates depleted body iron stores 1
• Transferrin saturation 13% is well below the 16–20% cutoff, confirming severely impaired iron delivery to bone marrow 1
• A ferritin <15 μg/L has 99% specificity for absolute iron deficiency; your patient's value of 23 ng/mL sits just above this threshold but still clearly indicates depletion 1

Immediate Treatment Protocol

Start oral iron supplementation today—do not wait for investigation results:

• Prescribe ferrous sulfate 65 mg elemental iron daily (or 60–65 mg every other day if gastrointestinal side effects occur) 1
• Alternate-day dosing improves absorption by 30–50% and reduces constipation, nausea, and diarrhea 1
• Take on an empty stomach for optimal absorption, or with meals if symptoms develop 1
• Expected response: Hemoglobin should rise by ≥10 g/L within 2 weeks; absence of this rise suggests malabsorption, non-compliance, or ongoing blood loss 1

Mandatory Gastrointestinal Investigation

In adult men and postmenopausal women, bidirectional endoscopy (gastroscopy + colonoscopy) is required as first-line investigation, regardless of whether anemia is present:

• Age and sex are independent predictors of gastrointestinal cancer risk in iron deficiency 1
• Nine percent of patients over 65 years with iron deficiency have gastrointestinal malignancy 2
• The British Society of Gastroenterology provides a strong recommendation (100% consensus) that men and postmenopausal women with newly diagnosed iron deficiency should undergo gastroscopy and colonoscopy 1, 3
• Do not use fecal occult blood testing—it has no role in risk stratification for patients with confirmed iron deficiency 3

Before endoscopy, complete these screening tests:

• Celiac disease serologic testing (tissue transglutaminase IgA antibodies)—celiac disease accounts for 3–5% of iron deficiency cases and causes treatment failure when missed 1, 3
• Non-invasive Helicobacter pylori testing (stool antigen or urea breath test)—the organism impairs iron absorption 1, 3

Follow-Up and Monitoring

• Recheck CBC and ferritin at 8–10 weeks to assess therapeutic response 1
• Target ferritin >100 ng/mL to fully restore iron stores and prevent recurrence 1
• Continue oral iron for 3 months after hemoglobin normalizes—absorbed iron is initially directed to red cell production, and storage compartments refill only after hemoglobin corrects 1

Indications to Switch to Intravenous Iron

Consider intravenous ferric carboxymaltose (15 mg/kg, maximum 1000 mg per dose) if any of the following develop:

• Severe oral iron intolerance (marked nausea, constipation, diarrhea) 1
• Confirmed malabsorption (celiac disease, inflammatory bowel disease, post-bariatric surgery) 1
• Lack of hemoglobin response after 8–10 weeks of adequate oral iron 1
• Ongoing blood loss exceeding oral replacement capacity 1
• Chronic inflammatory conditions (chronic kidney disease, heart failure, cancer) 1

IV iron produces reticulocytosis within 3–5 days and yields a mean hemoglobin increase of approximately 8 g/L over 8 days, demonstrating superior efficacy in these populations 1

Critical Pitfalls to Avoid

• Do not assume dietary causes or defer investigation—in men and postmenopausal women, iron deficiency may be the sole presenting sign of gastrointestinal malignancy 1, 3
• Do not stop iron therapy once hemoglobin normalizes—an additional 3 months of supplementation is required to achieve ferritin >100 ng/mL 1
• Do not overlook celiac disease screening—its 3–5% prevalence in iron deficiency makes it a frequent cause of treatment failure 1
• Do not delay endoscopy in high-risk patients—age ≥50 years, alarm symptoms (abdominal pain, weight loss, altered bowel habits, visible blood), or lack of response to oral iron all mandate urgent evaluation 1, 3