What is the diagnosis and treatment plan for a patient with microcytic anemia and low hemoglobin level, as indicated by CBC results?

Microcytic Hypochromic Anemia: Iron Deficiency Anemia

This patient has classic iron deficiency anemia and requires oral iron supplementation with ferrous sulfate 200 mg three times daily for at least three months after hemoglobin normalizes, along with mandatory investigation to identify the source of iron loss. 1

Diagnostic Interpretation

The CBC results demonstrate a clear pattern of iron deficiency anemia:

• Microcytic pattern: MCV 70.3 fL (markedly low, reference 83-101 fL) with MCH 23.1 pg (low, reference 27-32 pg) 2
• Elevated RDW: 14.5% (high, reference 11.6-14%) combined with low MCV strongly distinguishes iron deficiency from thalassemia minor 1, 2
• Anemia: Hemoglobin 10.70 g/dL (low, reference 12-15 g/dL) with hematocrit 32.5% (low, reference 36-46%) 2
• Normal white blood cell and platelet counts: Rules out bone marrow failure or myelodysplastic processes 3

The combination of low MCV with elevated RDW >14.0% is pathognomonic for iron deficiency anemia, whereas thalassemia minor typically presents with low MCV but RDW ≤14.0% 1

Essential Next Step: Confirm Iron Deficiency

Serum ferritin is the single most useful test to confirm iron deficiency 1, 4:

• Ferritin <15 μg/L indicates absent iron stores 1
• Ferritin <30 μg/L indicates low body iron stores 1
• Ferritin <45 μg/L provides optimal sensitivity and specificity for iron deficiency 1, 2

If ferritin is normal or elevated, measure transferrin saturation (TSAT) and serum iron to differentiate from anemia of chronic disease or genetic disorders 1, 5

Treatment Protocol

First-Line Oral Iron Therapy

Prescribe ferrous sulfate 200 mg (approximately 65 mg elemental iron) three times daily 1, 2:

• Take separately from meals to maximize absorption 6
• Continue for at least three months after hemoglobin normalizes to fully replenish iron stores 1, 2
• Add ascorbic acid (vitamin C) 200-500 mg with each dose to enhance absorption 2

Alternative formulations if gastrointestinal side effects occur 1, 2:

• Ferrous gluconate
• Ferrous fumarate

Expected Response and Monitoring

Hemoglobin should rise ≥1 g/dL within 2 weeks 2:

• This confirms iron deficiency as the cause 1
• Expect at least 2 g/dL increase within 4 weeks 1, 2

Monitoring schedule 1, 2:

• Check hemoglobin, hematocrit, MCV, and MCH at 2 weeks
• Recheck at 4 weeks
• Monitor at 3 months, then every 3 months for the first year
• Annual monitoring thereafter

When to Consider Intravenous Iron

Switch to IV iron if 1, 2:

• Malabsorption is documented (celiac disease, H. pylori infection, autoimmune atrophic gastritis) 1
• Patient cannot tolerate oral iron despite trying alternative formulations
• No hemoglobin response after 4 weeks of adequate oral therapy
• Ongoing blood loss exceeds oral replacement capacity

Mandatory Investigation for Underlying Cause

Critical: Identifying the source of iron loss is non-negotiable 1, 2:

In Non-Menstruating Women (Postmenopausal)

• Fast-track gastrointestinal referral warranted if hemoglobin <10 g/dL to exclude malignancy 1, 2
• Upper and lower endoscopy to evaluate for gastrointestinal blood loss 1

In Menstruating Women

• Assess menstrual blood loss (heavy menstrual bleeding is the most common cause) 1
• Still investigate gastrointestinal sources if menstrual losses don't fully explain severity 1

Additional Investigations

• Screen for celiac disease if malabsorption suspected 1
• Test for H. pylori infection 1
• Evaluate dietary history for inadequate iron intake 1

Differential Diagnosis Considerations

When to Consider Genetic Disorders

Genetic disorders are unlikely in this case given the elevated RDW and typical presentation, but consider if 7:

• Extreme microcytosis (MCV <70 fL) with family history 7
• Failure to respond to adequate oral iron therapy 1
• Low-to-normal ferritin with remarkably low TSAT (suggests IRIDA) 1
• Normal iron studies with persistent microcytosis (suggests thalassemia) 1

Thalassemia Minor

• Order hemoglobin electrophoresis if MCV disproportionately low relative to degree of anemia, appropriate ethnic background, or normal iron studies 1
• Thalassemia typically shows MCV <70 fL with normal or near-normal RDW 1

Anemia of Chronic Disease

• TSAT <20% with ferritin >100 μg/L suggests anemia of chronic disease rather than iron deficiency 1

Critical Pitfalls to Avoid

Do not assume all microcytic anemia is iron deficiency 1:

• Always confirm with ferritin before starting iron therapy
• Unnecessary iron therapy in thalassemia or anemia of chronic disease can cause iron overload

Do not treat without investigating the source 1, 2:

• Iron deficiency in adults always requires explanation
• Missing gastrointestinal malignancy is a serious error

Do not stop iron therapy too early 2, 6:

• Continue for at least 3 months after hemoglobin normalizes to replenish stores
• Premature discontinuation leads to recurrence

Do not overlook combined deficiencies 1:

• Check B12 and folate if response to iron is suboptimal
• Combined deficiencies can mask each other