What is the best treatment approach for an adult patient with iron deficiency anemia, characterized by a low iron percentage saturation of 6%, hypochromic anemia (hemoglobin 10.1 g/dL) and mild anemia (hematocrit 32.1%), who is asymptomatic and stable?

Treatment of Iron Deficiency Anemia with Transferrin Saturation 6%, Hemoglobin 10.1 g/dL, Hematocrit 32.1%

Start oral iron replacement immediately with ferrous sulfate 65 mg elemental iron once daily (or alternate days if not tolerated), and simultaneously investigate the underlying cause with bidirectional endoscopy (gastroscopy and colonoscopy) if the patient is male or a postmenopausal woman. 1

Immediate Iron Replacement Strategy

Your patient has absolute iron deficiency anemia (transferrin saturation <20% defines this) with moderate anemia (Hb 10.1 g/dL), requiring prompt treatment even while asymptomatic. 1

Oral Iron Therapy (First-Line)

• Initiate ferrous sulfate 200 mg tablet (65 mg elemental iron) once daily, taken on an empty stomach for optimal absorption. 1
• If gastrointestinal side effects occur, switch to alternate-day dosing (every other day), which maintains similar total iron absorption while reducing adverse effects by 35-45%. 1
• Alternative formulations include ferrous fumarate 210 mg (69 mg elemental iron) or ferrous gluconate 300 mg (37 mg elemental iron) if ferrous sulfate is not tolerated. 1

Monitoring Response

• Check hemoglobin at 4 weeks to confirm response (expected rise ≥10 g/L within 2 weeks is highly suggestive of true iron deficiency). 1, 2
• Continue iron for 3 months after hemoglobin normalizes to adequately replenish bone marrow iron stores. 1, 2
• Monitor blood counts every 6 months initially after treatment completion to detect recurrent anemia. 1

Mandatory Investigation for Underlying Cause

Do not defer investigation while awaiting iron response unless colonoscopy is imminent. 1

Essential Workup

• Bidirectional endoscopy (gastroscopy AND colonoscopy) is first-line investigation in men and postmenopausal women with new iron deficiency anemia, as gastrointestinal malignancy must be excluded. 1, 2
• Urinalysis or urine microscopy to exclude renal blood loss. 1
• Celiac disease serological screening (tissue transglutaminase antibodies), as celiac disease is found in 3-5% of iron deficiency anemia cases. 1
• Consider Helicobacter pylori testing if atrophic gastritis is suspected. 3

Investigation Threshold

Investigation should be considered at any level of anemia in the presence of iron deficiency, though the urgency increases with more severe anemia (Hb <110 g/L in men, <100 g/L in non-menstruating women per NICE guidelines). 1

When to Consider Intravenous Iron

Parenteral iron is indicated if: 1, 4

• Oral iron is not tolerated despite alternate-day dosing
• No hemoglobin response after 4 weeks of adequate oral therapy (suggesting malabsorption)
• Ongoing blood loss is identified
• Chronic inflammatory conditions are present (though not mentioned in your case)

Critical Pitfalls to Avoid

• Never withhold iron replacement while awaiting investigation results—treatment and investigation should proceed simultaneously. 1
• Do not assume asymptomatic status means treatment can be deferred—iron deficiency anemia at this level (Hb 10.1 g/dL) can cause subclinical cognitive impairment, exercise intolerance, and developmental issues in certain populations. 1, 4
• Do not use modified-release iron preparations—they are less well absorbed and more expensive than standard formulations. 1
• Avoid transfusion unless the patient becomes symptomatic or hemodynamically unstable, as oral iron is effective for this degree of anemia. 1

Patient-Specific Considerations

If this is a premenopausal woman, gastrointestinal investigation may be deferred initially if menorrhagia or recent pregnancy explains the iron deficiency, though the threshold for investigation should remain low if symptoms or family history of GI pathology exist. 1

If no response to oral iron occurs within 4 weeks, consider malabsorption (celiac disease, atrophic gastritis, post-bariatric surgery), ongoing blood loss, or non-compliance, and proceed to intravenous iron. 1, 4