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Leukocytosis is a topic covered in the 5-Minute Emergency Consult.

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  • Any elevation of total number of white blood cells (WBCs) beyond expected value
  • Normal range for total WBCs (/mm3):
    • Adults: 4,500–11,000
    • Children: WBC count decreases with age:
      • Infant, 1 wk old: 5,000–21,000
      • Toddler, 1 yr old: 6,000–17,500
      • Child, 4 yr old: 5,500–15,500
    • Pregnancy:
      • 1st trimester: 5,000–14,000
      • 2nd trimester: 5,000–15,000
      • 3rd trimester: 5,000–17,000
  • Normal ranges shift upward with:
    • Exercise
    • Female gender
    • Smoking
    • Daytime hours
  • Given wide range of normal values, numbers must be interpreted in clinical context
  • Specific subsets
  • Neutrophil predominance (neutrophilia):
    • Absolute neutrophil count >7,500/mm3
    • Half of circulating neutrophils are adherent to blood vessel walls. They can be rapidly released (demarginate) in response to acute stressors. This can double the WBC count.
    • An additional pool of mature neutrophils, immature metamyelocytes, and band neutrophils are stored in the bone marrow. These can be released increasing the neutrophil count typically during inflammation or infection. Release of immature forms results in a “left shift.”
  • Lymphocyte predominance (lymphocytosis)
    • Absolute lymphocyte count >4,000/mm3
    • Stored in the spleen, lymph nodes, thymus, and bone marrow. They are typically released in response to foreign antigens or viral infections
  • Hyperleukocytosis (WBC >100,000/mm3):
    • Seen primarily in hematologic malignancies
    • Associated with leukostasis which can lead to cerebral infarction, pulmonary insufficiency, death


  • CBC most common test ordered from the emergency department
  • Leukocytosis is one of the most commonly found lab abnormalities.
  • Elevated WBC count can be found in 17% of ED patients in whom a CBC is checked (Callaham)


  • Neutrophil predominance:
    • Demargination/stress reaction:
      • Stress
      • Exercise
      • Surgery
      • Seizures
      • Trauma
      • Hypoxia
      • Pain
      • Vomiting
    • Inflammation:
      • Rheumatoid arthritis
      • Gout
      • Inflammatory bowel disease
    • Infection, generally bacterial
    • Lab error
    • Labor
    • Leukemoid reaction (TB, Hodgkin, sepsis, metastatic CA)
    • Medications:
      • β-Agonist (epinephrine, cocaine, parenteral albuterol)
      • Corticosteroids
      • Lithium
      • Granulocyte colony stimulating factor
    • Metabolic disorders:
      • DKA
      • Thyrotoxicosis
      • Uremia
    • Malignancy, nonhematogenous
    • Myeloproliferative disorders:
      • Chronic myeloid leukemia
      • Polycythemia vera
    • Pregnancy
    • Rapid RBC turnover:
      • Hemorrhage
      • Hemolysis
    • Tissue necrosis:
      • Cancer
      • Burns
      • Infarction
  • Lymphocyte predominance:
    • Infection, generally viral, early stages:
      • Mononucleosis
      • VZV
      • CMV
      • Viral hepatitis
    • Bacterial infection, specifically:
      • Pertussis
      • TB
      • Syphilis
      • Rickettsia
      • Babesia
      • Bartonella
    • Hypothyroidism
    • Immunologic responses:
      • Immunization
      • Autoimmune diseases
      • Graft rejection
    • Lymphoproliferative disease:
      • Acute lymphocytic leukemia
      • Chronic lymphocytic leukemia
      • Non-Hodgkin lymphoma
    • Splenectomy

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Rosen, Peter, et al., editors. "Leukocytosis." 5-Minute Emergency Consult, 5th ed., Lippincott Williams & Wilkins, 2016. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307637/all/Leukocytosis.
Leukocytosis. In: Rosen P, Shayne P, Barkin AZ, et al, eds. 5-Minute Emergency Consult. 5th ed. Lippincott Williams & Wilkins; 2016. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307637/all/Leukocytosis. Accessed April 24, 2019.
Leukocytosis. (2016). In Rosen, P., Shayne, P., Barkin, A. Z., Wolfe, R. E., Hayden, S. R., Barkin, R. M., & Schaider, J. J. (Eds.), 5-Minute Emergency Consult. Available from https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307637/all/Leukocytosis
Leukocytosis [Internet]. In: Rosen P, Shayne P, Barkin AZ, Wolfe RE, Hayden SR, Barkin RM, Schaider JJ, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2016. [cited 2019 April 24]. Available from: https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307637/all/Leukocytosis.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Leukocytosis ID - 307637 ED - Rosen,Peter, ED - Shayne,Philip, ED - Barkin,Adam Z, ED - Wolfe,Richard E, ED - Hayden,Stephen R, ED - Barkin,Roger M, ED - Schaider,Jeffrey J, BT - 5-Minute Emergency Consult UR - https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307637/all/Leukocytosis PB - Lippincott Williams & Wilkins ET - 5 DB - Emergency Central DP - Unbound Medicine ER -