What is the appropriate next step in management for an adult with normal hemoglobin, low‑normal serum iron and total iron‑binding capacity, and low ferritin indicating early iron deficiency?

Management of Early Iron Deficiency with Normal Hemoglobin

Start oral iron supplementation immediately with ferrous sulfate 200 mg once daily (or equivalent) and initiate investigation for the underlying cause, as this patient has confirmed iron deficiency (ferritin 25 μg/L) that warrants both treatment and diagnostic workup regardless of normal hemoglobin. 1

Why This Patient Has Iron Deficiency

Your patient's laboratory values confirm iron deficiency despite normal hemoglobin:

• Ferritin 25 μg/L indicates depleted iron stores - while not severely deficient, this is below optimal levels and represents early/latent iron deficiency 2, 3
• Transferrin saturation of 38% (108/283) is actually normal, but the low ferritin is the most sensitive and specific marker for iron deficiency 1
• Normal hemoglobin (13.3 g/dL) does not exclude iron deficiency - iron stores become depleted before anemia develops 4

Immediate Management: Iron Replacement Therapy

Begin oral iron supplementation without delay:

• Ferrous sulfate 200 mg once daily (containing approximately 65 mg elemental iron) is the recommended first-line treatment 1
• Alternative preparations include ferrous gluconate or ferrous fumarate if ferrous sulfate is not tolerated 1
• Do not defer iron therapy while awaiting investigations 1
• Continue treatment for approximately 3 months after hemoglobin normalizes to replenish iron stores 1

Monitor response at 2-4 weeks:

• Expect hemoglobin rise of ≥10 g/L within 2 weeks if true iron deficiency 1
• Failure to respond suggests malabsorption, continued blood loss, or incorrect diagnosis 1, 5

Investigation for Underlying Cause

The following workup is essential even with normal hemoglobin:

Mandatory Initial Investigations

• Detailed history focusing on: 1

  • NSAID/aspirin use (common cause of occult GI bleeding) 1, 2
  • Dietary assessment for inadequate iron intake 1, 2
  • Menstrual history if premenopausal woman 1
  • Family history of malabsorption disorders 1

• Celiac disease screening with tissue transglutaminase (tTG) antibody - found in 3-5% of iron deficiency cases 1, 2

• Urinalysis or urine microscopy to exclude urinary tract bleeding 1

When to Pursue GI Investigation

The threshold for endoscopic evaluation depends on patient demographics:

• Men and postmenopausal women: Even with normal hemoglobin, iron deficiency warrants consideration of bidirectional endoscopy (gastroscopy and colonoscopy) as first-line GI investigation, particularly if no other cause is identified 1, 6

• Premenopausal women: If menstrual loss or dietary deficiency adequately explains the iron deficiency, initial trial of iron therapy with close monitoring is reasonable 1

  • However, women over age 45 should be investigated according to standard guidelines regardless of menstrual status 1

Critical Pitfalls to Avoid

• Do not assume dietary deficiency alone without excluding pathologic causes in men and postmenopausal women 2
• Do not delay investigation pending response to iron therapy in at-risk populations, as this may miss GI malignancy 2
• Remember dual pathology - approximately 10% of patients have lesions in both upper and lower GI tracts, so complete evaluation even if one source is found 1, 2
• Stop NSAIDs if clinically appropriate - these are common culprits for occult blood loss 1, 2

Follow-Up Strategy

• Recheck hemoglobin and iron studies at 3-4 weeks to confirm response 1
• Monitor hemoglobin every 3 months for one year, then annually 1
• Consider further investigation if hemoglobin/ferritin cannot be maintained with iron therapy 1