High white blood cell count

Date Updated: 12/15/2022

Definition

A high white blood cell count is an increase in cells in the blood that fight infections.

What's considered high in a white blood cell count varies from one lab to another. This is because laboratories set their own reference ranges based on the populations they serve. In general, for adults a count of more than 11,000 white blood cells in a microliter of blood is considered high.

Causes

A high white blood cell count usually means one of the following has increased the making of white blood cells:

An infection.
Reaction to a medicine.
A bone marrow disease
An immune system issue.
Sudden stress such as hard exercise.
Smoking.

Specific causes of a high white blood cell count include:

Allergy, especially severe allergic reactions
Asthma
Bacterial, viral, fungal or parasitic infections
Burns
Churg-Strauss syndrome
Medicines, such as corticosteroids and epinephrine
Hay fever (allergic rhinitis)
Leukemia
Lymphoma
Myelofibrosis (a bone marrow disorder)
Polycythemia vera
Pregnancy
Rheumatoid arthritis (inflammatory joint disease)
Sarcoidosis (collections of inflammatory cells in the body)
Smoking
Tuberculosis
Vasculitis
Whooping cough

When to see a doctor

A test a health care provider orders to diagnose a condition can reveal a high white blood cell count. A high white blood cell count is rarely found by chance.

Talk to your care provider about what your results mean. A high white blood cell count plus results from other tests might show the cause of your illness. Or you might need other tests for more information about your condition.