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What can affect the results of a white blood cells test?

by — Last updated: 2017-08-17 in Cardiovascular Disorders and Diseases
Reviewed by Medical Team — 2017-06-14

Table of Contents

White blood cells have nuclei, participate in protecting the body from infection, and consist of lymphocytes and monocytes with relatively clear cytoplasm, and three types of granulocytes, whose cytoplasm has granules.

Eating, physical activity, and stress can cause an increased WBC count, and pregnancy in the final month and labor may be associated with increased WBC levels as well. If you have had your spleen removed, you may have a persistent mildly to moderately increased white blood cell count.

The WBC count tends to be lower in the morning and higher in the late afternoon, and these counts are age-related as well.

On average, normal newborns and infants have higher WBC counts than adults.

It is common for the elderly to fail to develop leukocytosis as a response to infection.

There are many drugs that cause both increased and decreased WBC counts, so this fact is important to consider as well before reading the results of a white blood cell count.

A low WBC count (leukopenia) may indicate [12]:

  • Bone marrow failure, possibly due to infection or cancer 
  • Cancer and/or tumor
  • Fibrosis
  • The presence of a cytotoxic substance
  • Collagen-vascular diseases (such as lupus erythematosus, a disease of the liver or spleen),
  • Radiation
  • Crohn's disease
  • Infections, such as tuberculosis (TB) or certain viruses like HIV
  • Lupus (also called systemic lupus erythematosus
  • Rheumatoid arthritis
  • Some medicines, such as those that treat infections, high blood pressure, or seizures

A high WBC count (leukocytosis) may indicate infectious diseases, an inflammatory disease (such as rheumatoid arthritis or allergy), leukemia, severe emotional or physical stress, tissue damage, and anemia.

The Risks Of A White Blood Cells Count

Risks associated with having blood drawn are slight [13]:

  • Excessive bleeding
  • Fainting or feeling light-headed
  • Hematoma or blood accumulating under the skin
  • Bruising
  • Infection (a slight risk any time the skin is broken)
  • Multiple punctures to locate veins

Drugs that may increase WBC counts include [10]:

  • Epinephrine
  • Allopurinol
  • Aspirin
  • Chloroform
  • Heparin
  • Quinine
  • Corticosteroids
  • Triamterene

Medicines that may decrease WBC counts include [10]:

  • Antibiotics
  • Anticonvulsants
  • Antihistamines
  • Antithyroid drugs
  • Arsenicals
  • Barbiturates
  • Chemotherapeutic agents
  • Diuretics
  • Sulfonamides

Veins and arteries vary in size from one patient to another and from one side of the body to the other, so obtaining a blood sample from some people may be more difficult than from others. That is why each person that undergoes a WBC count test should talk to the doctor beforehand.

Once your doctor reads your results, he or she will know if you need treatment. A low white blood cell count usually requires further investigation and therapy.