A high level of white blood cells in the blood. A high white blood cell count can be caused by infection, reaction to a medicine, a bone marrow disease, an immune system issue, smoking or sudden stress such as hard exercise.

When to seek immediate medical care

See a health care professional immediately for the following symptoms:

  • Persistent fever.
  • High pulse rate.
  • Night sweats.

When to make a doctor's appointment

Make an appointment to see a health care professional for:

  • Increased fatigue.
  • Recurrent infections.

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