White blood cells, or leukocytes, are one of the main components of human blood. They act as part of the immune system, defending the body against diseases and infections. When the body has excess white blood cells (leukocytosis), it may signal infection, inflammation, or other immune problems.

Elevated White Blood Cells (Leukocytosis)

A person is considered to have excess white blood cells, or leukocytosis, when a blood test shows a white blood cell count above 11,000 cells per microliter. In many situations, a higher white blood cell level is a normal response and not cause for alarm. It usually indicates the body is mounting a defense against infection or inflammation. Even so, some situations require attention, particularly when excess white blood cells occur alongside symptoms of more serious illness.

Causes of Elevated White Blood Cells 

White blood cells include five types: neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Depending on which type is elevated, excess white blood cells can be linked to different health problems, such as:

• Neutrophilia: infections and inflammatory processes
• Lymphocytosis: viral infections and leukemia
• Monocytosis: malignancy and various infections
• Eosinophilia: parasitic infections and allergies
• Basophilia: leukemia

Examples of inflammation and infections that can raise white blood cell levels include:

• Physical or emotional stress
• Chronic inflammation from injury, arthritis, and other conditions
• Immune disorders such as lupus and rheumatoid arthritis
• Thyroid disorders
• Tooth decay (dental caries)
• Drug reactions
• Allergic reactions
• Surgical removal of the spleen
• Viral, fungal, or parasitic infections
• Whooping cough (pertussis)
• Lupus

In addition to the conditions above, obese people and smokers also tend to have higher-than-normal white blood cell counts.

What to Watch Out for If You Have Elevated White Blood Cells

An elevated white blood cell level is often a normal finding. However, when the white blood cell count is very high and appears with other serious symptoms, it may point to a significant infection, blood cancers such as leukemia and lymphoma, or bone marrow disorders including polycythemia vera and myelofibrosis.

If elevated white blood cell levels come with symptoms such as fever, fatigue that persists despite rest, unintended weight loss, frequent night sweats, itching, dizziness and headaches, joint pain, pale skin, or shortness of breath, further tests are recommended so treatment can be started.

Because elevated white blood cell levels are often a reaction to other health conditions, your doctor will treat the underlying diseases that cause it. This may include chemotherapy, radiation, and other cancer therapies, or adjusting the dose of certain medicines to prevent adverse reactions.

Elevated white blood cell count generally reflects infection or inflammation somewhere in the body. Although this response can be normal, excess white blood cells can also signal an infection that warrants attention. See a doctor promptly if you notice these problems so you can receive appropriate care.

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