White Blood Cell Count Test

The white blood cell (WBC) count indicates the number of white blood cells in a sample of blood. This count provides a clue to the presence of illness. White blood cells are made in the bone marrow and protect the body against infection and aid in the immune response. If an infection develops, white blood cells attack and destroy the bacteria, fungus, or virus causing the infection. Conditions or medications that weaken the immune system, such as HIV infection or chemotherapy, cause a decrease in white blood cells. The WBC count detects dangerously low numbers of these cells. The WBC count is also used to help monitor the body's response to various treatments and to monitor bone marrow function.

PREPARATION FOR TEST

A blood sample is obtained by inserting a needle into a vein in the arm.

NORMAL FINDINGS

Total WBCs

  • Adult/Child greater than 2 years: 5000-10,000/mm3 or 5-10 x 109/L (SI units)

  • Child less than 2 years: 6200-17,000/mm3

  • Newborn: 9000-30,000/mm3

Differential Count / Absolute

  • Neutrophils 55-70% / 2500-8000 per mm3

  • Lymphocytes 20-40% / 1000-4000 per mm3

  • Monocytes 2-8% / 100-700 per mm3

  • Eosinophils 1-4% /  50-500 per mm3

  • Basophils 0.5-1.0% / 25-100 per mm3

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.

MEANING OF TEST

Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.

OBTAINING THE TEST RESULTS

It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.