In an adult patient with ferritin 14 ng/mL, transferrin saturation 12 %, and hemoglobin 11.2 g/dL, what is the most likely diagnosis and the appropriate initial work‑up and treatment?

Iron Deficiency Anemia: Diagnosis and Management

This patient has iron deficiency anemia (IDA) requiring immediate oral iron supplementation and investigation for the underlying cause of iron loss.

Diagnosis

The laboratory pattern confirms absolute iron deficiency anemia:

• Ferritin 14 ng/mL is below the diagnostic threshold of <15 ng/mL, which has 99% specificity for absolute iron deficiency 1, 2
• Transferrin saturation 12% is below the critical threshold of 16%, indicating insufficient iron available for erythropoiesis 2, 3
• Hemoglobin 11.2 g/dL meets WHO criteria for anemia in women (<12 g/dL) 1

This triad definitively establishes iron deficiency anemia requiring treatment 1, 2.

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Immediate Treatment Protocol

Start oral ferrous sulfate 200 mg (65 mg elemental iron) once daily immediately—do not delay while awaiting diagnostic workup 1, 4.

Optimizing Oral Iron Therapy

• Take on an empty stomach for maximal absorption, or with food if gastrointestinal side effects occur 1, 4
• Add vitamin C 500 mg with each iron dose to enhance absorption, especially critical given the severely low transferrin saturation of 12% 1, 4
• Once-daily dosing is superior to multiple daily doses because hepcidin remains elevated for ~48 hours after iron intake, blocking further absorption and increasing side effects without improving efficacy 1, 4
• Avoid tea and coffee for at least 1 hour after the iron dose, as these strongly inhibit absorption 4

Alternative Formulations

If ferrous sulfate is not tolerated, ferrous fumarate (106 mg elemental iron) or ferrous gluconate (38 mg elemental iron) are equally effective alternatives 1, 4.

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Expected Response and Monitoring

• Check hemoglobin at 4 weeks: expect a rise of approximately 2 g/dL (≥10 g/L) 1, 4
• Failure to achieve ≥10 g/L rise by 2 weeks predicts overall treatment failure and requires reassessment for malabsorption, ongoing blood loss, or need for IV iron 4
• Continue oral iron for 3 months after hemoglobin normalizes to fully replenish iron stores; total treatment duration is typically 6–7 months 1, 4
• Monitor hemoglobin and red cell indices every 3 months for the first year, then again after another year 1, 4

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Mandatory Investigation of Underlying Cause

For Adult Men and Postmenopausal Women

Urgent bidirectional endoscopy (upper endoscopy + colonoscopy) is mandatory because iron deficiency may be the sole manifestation of gastrointestinal malignancy 1, 4.

For Premenopausal Women

GI investigation is conditional rather than mandatory 1, 2:

1. Assess menstrual blood loss first: menorrhagia, pregnancy, and breastfeeding account for iron deficiency in 5–10% of menstruating women 1, 2
2. Screen for celiac disease with tissue transglutaminase IgA antibodies; celiac disease is present in 3–5% of iron deficiency cases and can cause treatment failure if missed 1, 4
3. Test for Helicobacter pylori non-invasively (stool antigen or urea breath test) 1, 4

Reserve Bidirectional Endoscopy For:

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

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When to Switch to Intravenous Iron

Switch to IV iron if any of the following are present 1, 4:

• Intolerance to at least two different oral iron preparations (ferrous sulfate, ferrous fumarate, ferrous gluconate) 1, 4
• Ferritin fails to improve after 4 weeks of compliant oral therapy 1, 4
• Active inflammatory bowel disease with hemoglobin <10 g/dL, because inflammation-induced hepcidin severely impairs oral iron absorption 1, 4
• Post-bariatric surgery patients due to disrupted duodenal absorption mechanisms 1, 4
• Celiac disease with inadequate response to oral iron despite strict gluten-free diet adherence 1, 4
• Ongoing gastrointestinal blood loss exceeding oral replacement capacity 1, 4

Preferred IV Iron Formulations

Choose IV iron preparations that replace iron deficits in 1–2 infusions to minimize risk and improve convenience 1, 4:

• Ferric carboxymaltose: 750–1000 mg per 15-minute infusion; two doses ≥7 days apart provide 1500 mg total 4
• Ferric derisomaltose: 1000 mg as a single infusion 4
• Avoid iron dextran as first-line due to higher anaphylaxis risk (0.6–0.7%) 4

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Critical Pitfalls to Avoid

• Do not prescribe multiple daily doses of oral iron; this increases side effects without improving efficacy due to hepcidin-mediated absorption blockade 1, 4
• Do not stop iron therapy when hemoglobin normalizes; continue for an additional 3 months to replenish stores 1, 4
• Do not persist with oral iron beyond 4 weeks without a hemoglobin rise; reassess for malabsorption, ongoing loss, or need for IV iron 1, 4
• Do not overlook vitamin C supplementation when oral iron response is suboptimal 1, 4
• Do not overlook celiac disease screening; its 3–5% prevalence in iron deficiency cases can lead to treatment failure if not identified 1, 4
• Do not delay endoscopic evaluation in high-risk patients (age ≥50, alarm symptoms, treatment failure), as GI malignancy can present solely with iron deficiency 1, 4