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Hemoglobin 8 g/dL with Normal RBC Count: Microcytic Anemia Workup

Hb 8 g/dL (normal: men 13.5–17.5, women 12–15.5) with normal RBC count (4.49 M/µL) indicates microcytic anemia (low MCV = Hb/RBC ratio).

Meaning

RBCs are normal in number but small and pale (low MCH, MCHC). Each carries insufficient hemoglobin.

Differential Diagnosis

CauseKey LabsClinical Clues
Iron Deficiency (IDA)Low ferritin (< 30), high TIBC, low TSAT%, high RDWMenorrhagia, GI blood loss, pregnancy, vegan diet, malabsorption
Thalassemia TraitNormal/high ferritin, normal TIBC, very low MCV (< 70), high RBC count, HbA₂ > 3.5% (β-thal)Ethnic risk (Mediterranean, Asian, African), family history, asymptomatic
Anemia of Chronic DiseaseLow/normal ferritin, low TIBC, normal/high hepcidin, normal RDWUnderlying inflammation (RA, CKD, cancer, infection)
Sideroblastic AnemiaRing sideroblasts on marrow, high ferritin, high TSAT%Alcohol, lead, drugs (isoniazid), genetic (X-linked ALAS2)

Diagnostic Algorithm

  1. Ferritin (if < 30 → IDA; if > 100 → not IDA).
  2. If ferritin 30–100 (equivocal): TSAT%, CRP, soluble transferrin receptor.
  3. Hemoglobin electrophoresis (thalassemia screen).
  4. If unexplained: consider marrow, genetic testing.

Treatment

  • IDA: Oral iron (ferrous sulfate 325 mg TID) + vit C; IV iron if intolerant/malabsorption/severe. Treat source of loss.
  • Thalassemia trait: No treatment; genetic counseling.
  • ACD: Treat underlying inflammation; ESA if CKD.

Hb 8 g/dL warrants prompt evaluation. Do not self-treat with iron without confirmation.

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