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


4 mechanisms:

  1. Loss of RBCs by hemorrhage (e.g. GI bleed)
  2. Increased destruction (SCD, hemolytic anemia)
  3. Impaired production (iron deficiency, folate deficiency, B12 deficiency, aplastic anemia/myelodysplastic syndrome)
  4. Dilutional (rapid IVF infusion)

Clinical Features

General Anemia Symptoms

  • Most patients begin to be symptomatic at ~7gm/dL
  • Weakness, fatigue, lethargy, dyspnea on exertion, palpitations
  • Skin, nail bed, mucosal pallor
  • Widened pulse pressure
  • Jaundice, hepatosplenomegaly (hemolysis)
  • Peripheral neuropathy (B12 deficiency)

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)

  • Vitamin B12/folate deficiency
  • Drugs (chemo)
  • HIV


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.
Algorithm for the Evaluation of 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
    • RBC count low: Anemia chronic disease, hypothyroidism, Vitamin C deficiency
    • RBC count nl or high: Thalassemia

Normocytic Anemia (81-100 fL)

  • Retic count normal
    • RDW normal: Anemia chronic disease, anemia of renal insufficiency
    • RDW high: Iron, Vit B12, or folate deficiency
  • Retic count high
    • Coombs Positive: Autoimmune cause
    • Coombs negative: G6PD, SCD, spherocytosis, microangiopathic hemolysis

Macrocytic Anemia (MCV>100 fL)

  • RDW high: Vit B12 or folate deficiency
  • RDW normal: ETOH abuse, liver disease, hypothyroidism, drug induced, myelodysplasia



  • 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 restrictve 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

External Links


  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