• Affects 1/3 of the world's population
  • Most common causes are uterine and GI bleeding


4 mechanisms:

Clinical Features

General Anemia Symptoms

Differential Diagnosis


RBC Loss

  • Hemorrhage

RBC consumption (Destruction/hemolytic)

Impaired Production (Hypochromic/microcytic)

  • Iron deficiency
  • Anemia of chronic disease
  • Thalassemia
  • Sideroblastic anemia

Aplastic/myelodysplastic (normocytic)

  • Marrow failure
  • Chemicals (e.g. ETOH)
  • Radiation
  • Infection (HIV, parvo)

Megaloblastic (macrocytic)


Severe anemia is defined as a hemoglobin level of 5 to 7 g/dL with symptoms of hypoperfusion including lactic acidosis, base deficit, shock, hemodynamic instability, or coronary ischemia[1]

Acute Anemia

  • Assess for any signs of bleeding or trauma before considering other causes of chronic anemia.

Chronic Anemia

  • CBC for evaluation, look at MCV
    • Microcytic: Iron Levels, Reticulocyte Count, Ferritin, TIBC
    • Macrocytic: Folate Level, B12 Level, Reticulocyte Count

Microcytic Anemia (<81 fL)

  • RDW high → evaluate Ferritin, which is a measurement of iron storage
    • Ferritin low: Iron deficiency anemia
    • Ferritin normal: Anemia chronic disease or sideroblastic anemia (e.g. lead poisoning)
  • RDW normal

Normocytic Anemia (81-100 fL)

Macrocytic Anemia (MCV>100 fL)


  • Transfusions
    • Consider if patient is symptomatic, hemodynamically unstable, hypoxic, or acidotic
    • Using a restrictive transfusion strategy (transfusing <6-8) has found to be beneficial, as liberal transfusion strategy (transfusing <10) not showing any benefit and has shown harm
      • GI bleeds using restrictive transfusion strategy saw a decreased mortality and rebleed rate
    • Always draw labs necessary for diagnosis prior to transfusing
    • 1 unit PRBCs should raise the Hgb by 1gm/dL
  • Iron-deficiency anemia
    • PO: Ferrous sulfate 325mg (65mg elemental iron) with Vitamin C (to aid in absorption)
    • IV: Ferrous Sucrose 300mg in 250mL NS over 2hrs


  • Depends on underlying cause of anemia

See Also

  • Transfusions
  • Myelophthisic Anemia
  • Microangiopathic Hemolytic Anemia (MAHA)


  1. Posluszny JA Jr, Napolitano LM. How do we treat life-threatening anemia in a Jehovah's Witness patient? Transfusion. 2014;54(12):3026-3034
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