What is the likely diagnosis and recommended management for a patient with UIBC (unsaturated iron‑binding capacity) 351 µg/dL, transferrin saturation (iron saturation) 6 %, serum iron 21 µg/dL, and ferritin 14 ng/mL?

Diagnosis: Iron Deficiency Anemia (IDA)

This patient has clear-cut iron deficiency anemia based on the laboratory values: ferritin 14 ng/mL (severely depleted iron stores), transferrin saturation 6% (markedly reduced), serum iron 21 µg/dL (low), and elevated UIBC 351 µg/dL (indicating increased iron-binding capacity from depleted stores). 1

Laboratory Interpretation

Your patient's iron panel demonstrates:

• Ferritin 14 ng/mL: Well below the diagnostic threshold of 45 ng/mL recommended for diagnosing iron deficiency in anemia 1, and even below the 15-20 ng/mL threshold indicating completely empty iron stores 2, 3
• Transferrin saturation 6%: Severely reduced (normal >20%), confirming inadequate iron availability for erythropoiesis 4
• UIBC 351 µg/dL: Elevated, which has superior diagnostic accuracy compared to transferrin saturation alone for detecting empty iron stores 2, 5
• Serum iron 21 µg/dL: Markedly low

The constellation of low ferritin, low transferrin saturation, low serum iron, and elevated UIBC definitively establishes iron deficiency without need for additional confirmatory testing.

Required Diagnostic Workup

You must identify the underlying cause of iron loss or malabsorption before simply treating with iron replacement. The evaluation should include:

For All Patients:

• Dietary assessment: Quantify iron intake from diet
• Medication review: NSAIDs, anticoagulants, antiplatelet agents causing occult GI bleeding
• Helicobacter pylori testing: Can cause iron malabsorption 1
• Celiac disease screening: Impairs iron absorption 1

Sex-Specific Evaluation:

• Premenopausal women: Detailed menstrual history (heavy menstrual bleeding is the most common cause), gynecologic evaluation for fibroids, endometriosis, or other causes of blood loss 6
• Men and postmenopausal women: Bidirectional endoscopy (upper and lower GI) is mandatory to exclude GI malignancy, inflammatory bowel disease, gastric antral vascular ectasia, celiac disease, or small bowel angioectasias 1, 4

Treatment Approach

Initial Iron Replacement:

Start with oral iron supplementation as first-line therapy unless contraindications exist 1, 4:

• Dosing: 100-200 mg elemental iron daily
• Timing: Take on empty stomach for optimal absorption; if not tolerated, take with meals (particularly with meat protein and 500 mg vitamin C to enhance absorption) 1
• Common formulations: Ferrous sulfate 325 mg (65 mg elemental iron) taken 2-3 times daily

When to Use Intravenous Iron:

Switch to IV iron if 1, 4:

• Intolerance to oral iron (nausea, abdominal pain, constipation)
• Malabsorption conditions (celiac disease, inflammatory bowel disease, prior gastric surgery)
• Severe anemia requiring rapid repletion
• Ongoing blood loss exceeding oral replacement capacity
• Chronic kidney disease (especially if on dialysis)
• Chronic heart failure (IV iron has prognostic benefit; oral iron should be avoided) 4

Monitoring and Follow-up

• Recheck complete blood count and iron studies in 4-6 weeks to assess response
• Continue iron replacement for 3-6 months after normalization to replete iron stores (target ferritin >50-100 ng/mL)
• Monitor for recurrence: Check iron studies every 3 months for the first year after correction, then periodically 4

Critical Pitfalls to Avoid

1. Do not assume menstrual bleeding is the cause in premenopausal women without proper evaluation—they can still have GI pathology
2. Do not overlook the need for GI investigation in men or postmenopausal women—this is mandatory
3. Do not use transferrin saturation alone—UIBC provides better diagnostic accuracy 2, 5
4. Do not stop iron replacement when hemoglobin normalizes—continue until iron stores are replete
5. In patients with inflammation (elevated CRP), ferritin may be falsely elevated; transferrin saturation and UIBC become more important for diagnosis 4