What is the appropriate management for a patient with microcytic anemia, characterized by low Hemoglobin (Hgb), low Hematocrit (HCT), and a low Mean Corpuscular Volume (MCV)?

Management of Microcytic Hypochromic Anemia

Start oral ferrous sulfate 324 mg (65 mg elemental iron) one to three times daily for at least three months after hemoglobin normalizes, as this is first-line treatment for the most common cause—iron deficiency anemia. 1

Immediate Diagnostic Workup

Your laboratory values (Hgb 9.4, MCV 76, MCH 22.6, MCHC 29.8) demonstrate classic microcytic hypochromic anemia that requires immediate investigation. 1

Essential first-line tests:

• Serum ferritin is the single most useful marker, with <45 μg/L providing optimal sensitivity and specificity for iron deficiency 2, 1
• Transferrin saturation (TSAT) should be added if ferritin appears falsely elevated due to inflammation; TSAT <16-20% confirms iron deficiency 2
• Red cell distribution width (RDW): elevated RDW >14.0% combined with low MCV strongly distinguishes iron deficiency from thalassemia minor 2, 1
• C-reactive protein to identify inflammation that may falsely elevate ferritin up to 100 μg/L 2

Treatment Algorithm

If Iron Deficiency Confirmed (Ferritin <45 μg/L, TSAT <20%)

Oral iron therapy:

• Ferrous sulfate 324 mg (65 mg elemental iron) one to three times daily 1
• Add ascorbic acid (vitamin C) 200-500 mg with each dose to enhance absorption 1
• Alternative formulations (ferrous gluconate or ferrous fumarate) if gastrointestinal side effects occur 2, 1
• Continue for at least three months after hemoglobin normalizes to fully replenish iron stores 2, 1

Expected response:

• Hemoglobin should rise ≥1 g/dL within 2 weeks, confirming iron deficiency 1
• Expect at least 2 g/dL increase within 4 weeks 2, 1

If No Response to Oral Iron After 4 Weeks

Consider intravenous iron if:

• Malabsorption documented (celiac disease, H. pylori, atrophic gastritis) 2
• True intolerance to oral preparations 1
• Ongoing blood loss exceeds oral replacement capacity 1

For IV iron: Use iron sucrose or iron gluconate, expecting hemoglobin increase of at least 2 g/dL within 4 weeks 2, 1

If Ferritin Normal/High with Microcytosis

Consider genetic disorders of iron metabolism or heme synthesis, particularly with:

• Extreme microcytosis (MCV <70) 2
• Family history of refractory anemia 3, 2
• Elevated ferritin and/or transferrin saturation 3
• Low TSAT with low-normal ferritin (>20 mg/L) 2

Specific genetic considerations:

• IRIDA (iron-refractory iron deficiency anemia): Remarkably low TSAT with low-to-normal ferritin, fails oral iron but may respond to IV iron 2
• X-linked sideroblastic anemia (ALAS2 defects): Trial of pyridoxine 50-200 mg daily initially, then 10-100 mg daily lifelong if responsive 2, 4
• SLC25A38 defects: Hematopoietic stem cell transplantation is the only curative option 2, 4

Mandatory Investigation for Underlying Cause

Critical pitfall: Never treat microcytic anemia without identifying the source of iron loss. 1

Investigate for:

• Gastrointestinal blood loss: Non-menstruating women with Hgb <10 g/dL warrant fast-track GI referral to exclude malignancy 2, 1
• Menstrual blood loss: Most common cause in premenopausal women 2
• Malabsorption disorders: Screen for celiac disease, H. pylori, autoimmune atrophic gastritis 2
• Dietary inadequacy: Particularly in vegetarians or those with restricted diets 2

Monitoring Schedule

• Check hemoglobin, hematocrit, MCV, and MCH at 2 weeks, 4 weeks, 3 months 1
• Continue monitoring every 3 months for the first year, then annually 2, 1
• Monitor serum ferritin and transferrin saturation to assess iron stores 2
• For patients receiving transfusions or long-term iron therapy, monitor for iron overload with liver MRI in specific cases 2

Critical Pitfalls to Avoid

• Do not assume all microcytic anemia is iron deficiency: Anemia of chronic disease (TSAT <20% with ferritin >100 μg/L), thalassemia, and sideroblastic anemia require different management 2
• Do not use ferritin alone in inflammatory states: It can be falsely elevated; add TSAT to the workup 2
• Do not overlook combined deficiencies: Iron deficiency can coexist with B12 or folate deficiency 2
• Order hemoglobin electrophoresis if: Microcytosis with normal iron studies, appropriate ethnic background, or MCV disproportionately low relative to degree of anemia 2