What is the most appropriate next step in management for an asymptomatic 50‑year‑old woman with neutrophilia, borderline monocytosis, low ferritin and low serum iron indicating iron‑deficiency?

Immediate Management of Iron Deficiency with Reactive Leukocytosis

Begin oral ferrous sulfate 325 mg (65 mg elemental iron) daily immediately while investigating the underlying cause of iron loss. 1, 2

Laboratory Interpretation

Your laboratory values confirm absolute iron deficiency:

• Ferritin 15 ng/mL sits precisely at the diagnostic threshold; values <15 μg/L have 99% specificity for depleted iron stores, and <30 μg/L definitively indicate low body iron 1, 3
• Serum iron 32 μg/dL is markedly reduced (normal ~50–170 μg/dL), reflecting insufficient circulating iron for erythropoiesis 1
• The neutrophil count of 11,210/μL represents reactive neutrophilia, a common hematologic response to iron deficiency that typically peaks in the third week of deficiency 1
• Monocyte count 1,004/μL falls within normal limits (200–950/μL) and does not indicate pathology 1

The combination of borderline-low ferritin with low serum iron in a 50-year-old woman mandates investigation for occult blood loss, particularly gastrointestinal sources. 4, 1

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Mandatory Diagnostic Work-Up

Non-Invasive Screening (Perform First)

• Screen for celiac disease with tissue transglutaminase IgA antibodies—celiac accounts for 3–5% of iron-deficiency cases and causes treatment failure when missed 4, 1
• Test for Helicobacter pylori using stool antigen or urea-breath test, as the organism impairs iron absorption 4, 1
• Calculate transferrin saturation (TSAT) if total iron-binding capacity is available: TSAT <16–20% confirms iron deficiency even when ferritin appears borderline 4, 1

Endoscopic Evaluation (Reserve for Specific Indications)

Bidirectional endoscopy (upper GI + colonoscopy) is mandatory if:

• Age ≥50 years (you meet this criterion—higher malignancy risk) 4, 1
• Gastrointestinal symptoms present (abdominal pain, altered bowel habits, visible blood) 4, 1
• Positive celiac or H. pylori testing requiring confirmation 4, 1
• Failure to respond to adequate oral iron after 8–10 weeks 4, 1
• Strong family history of colorectal cancer 4, 1

Because you are 50 years old, upper endoscopy with duodenal biopsies and colonoscopy should be scheduled promptly to exclude gastric cancer, peptic ulcer disease, colonic carcinoma, polyps, and angiodysplasia—all common occult bleeding sources in this age group. 4, 1

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Oral Iron Supplementation Protocol

• Start ferrous sulfate 325 mg (65 mg elemental iron) once daily 1, 2
• Alternate-day dosing (60–65 mg every other day) improves absorption by 30–50% and reduces gastrointestinal side effects (nausea, constipation, diarrhea) compared to daily dosing 1
• Take on an empty stomach for optimal absorption; if gastrointestinal symptoms occur, take with meals 1
• Expected response: hemoglobin should rise ≥10 g/L within 2 weeks, confirming iron deficiency as the cause 1

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Follow-Up and Monitoring

• Repeat 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 to replenish storage iron; stopping prematurely leads to rapid relapse 1
• If no improvement after 8–10 weeks, consider malabsorption (celiac disease, inflammatory bowel disease), non-compliance, ongoing blood loss, or need for intravenous iron 4, 1

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When to Switch to Intravenous Iron

Intravenous ferric carboxymaltose (15 mg/kg, max 1000 mg per dose) is indicated if: 1

• Oral iron intolerance (severe nausea, constipation, diarrhea) 1
• Confirmed malabsorption (celiac disease, inflammatory bowel disease, post-bariatric surgery) 1
• Ongoing blood loss exceeding oral replacement capacity 1
• Lack of hemoglobin response after 8–10 weeks of adequate oral therapy 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 ≈8 g/L over 8 days, demonstrating superior efficacy in these populations. 1

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Critical Pitfalls to Avoid

• Do not attribute iron deficiency in a 50-year-old woman solely to dietary insufficiency or menstrual loss—gastrointestinal malignancy must be excluded with endoscopy 4, 1
• Do not overlook celiac disease screening; its 3–5% prevalence in iron-deficiency cases leads to treatment failure when missed 4, 1
• Do not discontinue iron therapy once hemoglobin normalizes—an additional 3 months of supplementation is required to achieve ferritin >100 ng/mL 1
• Do not delay endoscopic evaluation in patients ≥50 years, as gastrointestinal malignancy can present solely with iron deficiency before anemia develops 4, 1
• Do not assume reactive neutrophilia indicates infection or malignancy—it is a common benign response to iron deficiency that resolves with iron repletion 1