High White Blood Cell Count

Leukocytosis, or high white blood cell count, can indicate a range of conditions, including infections, inflammation, injury and immune system disorders. A complete blood count (CBC) is usually performed to check for leukocytosis. Treating the underlying condition usually reduces your white blood cell count.


What is leukocytosis?

Leukocytosis means you have a high white blood cell count. This means you have more white blood cells than normal. Leukocytosis is a normal immune response and isn’t always a cause for concern. Most of the time, it means that your body is fighting off infection or inflammation. However, there are times when a high white blood cell count could indicate something more serious, such as leukemia.

Types of leukocytosis

There are five types of white blood cells (leukocytes), so there are five types of leukocytosis, depending on which type of cell is affected:

  • Neutrophilia leukocytosis is caused by a high number of neutrophils (the most plentiful type of white blood cell, which helps resolve infections and heal damaged tissues).
  • Lymphocytosis refers to high levels of lymphocytes (white blood cells that protect your lymphatic system).
  • Monocytosis is caused by a high number of monocytes (white blood cells that boost your immune responses).
  • Eosinophilia refers to high levels of eosinophils (white blood cells that play a role in fighting infections and inflammation). Eosinophilia is common and is often related to allergies, parasitic infections or autoimmune disorders.
  • Basophilia, the rarest form of leukocytosis, is characterized by an increased number of basophils (white blood cells that play a role in fighting parasitic infections, preventing blood clotting and responding to allergic reactions).

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What does a high white blood cell count mean?

White blood cells are an important and necessary part of your immune system. Produced in your bone marrow, they defend your body against infections and disease. But, when there are too many white blood cells, it usually means you have infection or inflammation in your body. Less commonly, a high white blood cell count could indicate certain blood cancers or bone marrow disorders.

What is considered a high white blood cell count?

Typically, if there are more than 11,000 white blood cells in a microliter of your blood, it’s considered leukocytosis.

High white blood cell count during pregnancy

A high blood cell count during pregnancy is normal. Your body is simply experiencing the stress of carrying a baby. Your healthcare provider will run routine blood tests throughout your pregnancy to make sure nothing out of the ordinary is going on.

Is leukocytosis a blood cancer?

No. Leukocytosis refers to a high white blood cell count, which can occur for a number of reasons. Rarely, a high white blood cell count can be a symptom of certain blood cancers, such as acute myeloid leukemia, chronic myelogenous leukemia and chronic lymphocytic leukemia.


Symptoms and Causes

What are the signs and symptoms of leukocytosis?

Many leukocytosis symptoms could indicate an infection or something more serious, such as lymphoma or leukemia. Common warning signs include:

Easy bruising may indicate thrombocytopenia (low platelet count) or severe acute leukemia. In cases of severe acute leukemia, extremely elevated white blood cells can thicken your blood and decrease blood flow. As a result, hyperviscosity syndrome can develop. This condition can cause serious health problems, such as stroke, internal bleeding or vision impairment.

What causes leukocytosis?

Leukocytosis is most commonly caused by infection or inflammation. Other high white blood cell count causes may include:

Less commonly, leukocytosis is associated with:


Diagnosis and Tests

How is leukocytosis diagnosed?

Your healthcare provider will perform an exam and ask about your symptoms and medical history. They’ll also order a complete blood count (CBC). This common blood test checks for red blood cells, white blood cells and platelets in your blood. A CBC can tell your healthcare provider if you have certain conditions or infections. In some cases, you might need a bone marrow test to confirm your diagnosis.

Management and Treatment

How is leukocytosis treated?

Treatment for leukocytosis varies depending on what caused the condition in the first place. For example, if you have a high white blood cell count due to a bacterial infection, then your healthcare provider will prescribe antibiotics. If leukocytosis is associated with an allergic reaction, then you’ll probably need antihistamines. Other common high white blood cell count treatments include:

  • Medications to reduce stress or anxiety.
  • Anti-inflammatory medications.
  • Inhalers to treat asthma.
  • IV fluids to improve blood flow.
  • Leukapheresis, a procedure to quickly reduce the number of white blood cells in your blood.
  • Cancer treatments, such as chemotherapy, radiation therapy or stem cell transplants.

In some cases, your white blood cell count may return to normal without intervention.

How long does it take to recover from leukocytosis treatment?

It depends on which type of treatment you receive. In most instances, you can recover from leukocytosis in two to four weeks. If you’re undergoing cancer treatment, it could take longer.


Can I prevent leukocytosis?

Remember that leukocytosis is a normal immune response, so it doesn’t always need to be prevented. For example, your white blood cells increase when your body needs to fight off infection or inflammation. But, there are things you can do to keep your white blood cell count in a healthy range:

  • Wash your hands frequently to reduce the risk of infection.
  • Avoid potential allergens.
  • Don’t smoke.
  • Practice good dental hygiene.
  • Visit your dentist every six months.
  • Take all medications as directed by your healthcare provider.
  • Find ways to reduce your stress levels, like mindfulness or meditation.
  • Seek treatment for anxiety or depression as needed.

Outlook / Prognosis

What can I expect if I have leukocytosis?

If you have leukocytosis, your healthcare provider will run tests to determine why your white blood cell counts are elevated. Once the root cause has been identified, your healthcare provider will recommend appropriate treatment.

Living With

When should I see my healthcare provider?

It’s important to call your healthcare provider if something doesn’t seem quite right. Make an appointment if you experience:

  • Fever.
  • Easy bruising.
  • Excess bleeding.
  • Nausea and vomiting.
  • Fatigue.
  • Unexplained weight loss.
  • Poor appetite.
  • Soaking night sweats on a regular basis.

When should I go the ER?

If you develop any of the following symptoms, call 911 or head to your nearest emergency room:

  • Stroke symptoms, such as confusion, dizziness or facial drooping.
  • Chest pain.
  • Difficulty breathing.
  • Tingling in your arms, legs or abdomen.
  • Sudden back pain.
  • Bleeding that doesn’t stop.

A note from Cleveland Clinic

Most of the time, leukocytosis is a normal immune response caused by infection or inflammation. Sometimes, it’s associated with stress, anxiety or pregnancy. In some cases, however, a high white blood cell count could mean something more serious. That’s why it’s important to talk to your healthcare provider. They can determine the cause of leukocytosis and decide whether treatment is necessary.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 01/19/2022.

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