Low White Blood Cell Count (Leukopenia) Symptoms and Causes

Human blood has many different cells, substances and chemicals floating within it, all of which play different roles in maintaining and restoring health. One of these components is white blood cells, which are also known as leukocytes. These cells help to protect the body and fight infections. Too much or too little of these white blood cells may be a sign of disease and can also affect the body’s ability to defend itself.

What is Leukopenia?

Leukopenia is the medical term for low white blood cell levels. These cells are also known as leukocytes, hence the term leukopenia (-penia means abnormal reduction). The level of white blood cells can vary to some degree within the normal range. Some people may have slightly lower than normal levels without experiencing any associated health problems.

Read more on high white blood cell count.

There are many different types of white blood cells. A low count of a certain white blood cell, for example the neutrophils, is known as neutropenia. Similarly white blood cells are one component of all the blood cells, also referred to as the complete blood cell count (CBC). Leukopenia is a low count of the total white blood cells in circulation. On the other extreme, a high white blood cell count level is known as leukocytosis.

Signs and Symptoms of Leukopenia

There may not always be immediate signs and symptoms of a low white blood cell count. Often it is discovered upon performing blood tests like a complete blood count (CBC). The threshold for adults is a white blood cell count of 4,000 cells per microliter of blood. Any reading lower than this level would be leukopenia (low white blood cell count). Factors like ago do play a role as the threshold varies for children.

The signs and symptoms of low white blood cell count can be vague and non-specific. It may also vary depending on the underlying disease that is present at the time. These signs and symptoms may include:

  • Cough
  • Diarrhea
  • Fatigue
  • Fever
  • Night sweats
  • Shortness of breath
  • Skin rash
  • Swollen lymph nodes
  • Unintentional weight loss

One or more symptoms may be present. Recurrent infections, even different types of infections, may also be a sign of a low white blood cell count.

WARNING: A low white blood cell count in itself may not be life-threatening but it can increase the risk of serious diseases and infections. Therefore it is important that a low white white blood cell count is regularly monitored by a medical professional and appropriately treated where possible. Do not wait for signs or symptoms of serious diseases to arise before seeking medical attention.

Causes of Low White Blood Cells

White blood cells are produced in the bone marrow on a constant basis and released into circulation. New cells replace the old cells that become worn out or die. White blood cells are also kept in reserve in organs like the spleen and then sent to areas of the body that it need it most during certain diseased states, like with an infection. A low white blood cell count is usually an indication of either inadequate production of the cells or rapid breakdown of the white blood cells. Some of the possible reasons for a low white blood cell count has been discussed below.

Read more on granulocytes and lymphocytes.


Prolonged and widespread infections can strain and deplete the white blood cell resources in the body. Some viral diseases can also disrupt the bone marrow production of white blood cells. Infection like HIV may directly target and destroy certain white blood cells. The low white blood cell count can be further impacted by poor nutrition and certain drugs during an infection.


Cancers can affect white blood cell count in various ways. Some cancers can directly damage bone marrow tissue or disrupt the production of white blood cells, as is the case in leukemia. Cancer treatments like chemotherapy may also lead to low white blood cells count due to its action on circulating white blood cells and the bone marrow, while radiation therapy may destroy bone marrow tissue and white blood cells.


Certain autoimmune diseases can attack, damage and/or disrupt bone marrow or white blood cells. This may be seen in conditions like SLE (systemic lupus erythematosus) and rheumatoid arthritis. The disturbance may sometimes only be temporary and subside when the condition is in remission or properly managed.


There are certain conditions that may be present from birth which can lead to lower than normal bone marrow activity or disrupt the circulation of white blood cells. Kostmann’s syndrome is a congenital disorder where the bone marrow produces less neutrophils. In another congenital disorder known as myelokathexis, the neutrophils are unable to enter the bloodstream.


Several different medication can lead to low white blood cell count either by affecting the production of cells in the bone marrow or by destroying white blood cells. Other substances, like arsenic, may also lead to low white blood cell count as a result of poisoning.


The spleen is a reservoir for blood and for white blood cells. When needed, the spleen can then send out more white blood cells into the circulation. However, white blood cells maturation and storage can be affected in certain spleen conditions.


A lower than threshold level white blood cell may be observed in certain ethnicities. People of African or Middle Eastern ethnicity may have have lower white blood cell counts. This is considered normal and they may be healthy. However, a very low white blood cell count is still abnormal.

List of Conditions Causing Leukopenia

These are conditions where a low white blood cell count may occur.

  • AIDS (Acquire Immune Deficiency Syndrome)
  • Aplastic anemia
  • Cancer
  • Chemotherapy
  • Crohn’s disease
  • Drugs like certain antibiotics, antihistamines, corticosteroids, diuretics, thyroid drugs and other medication.
  • HIV infection
  • Hypersplenism
  • Infections, other
  • Leukemia
  • Liver disease
  • Kostmann’s syndrome
  • Malnutrition
  • Myelodysplastic syndromes
  • Myelokathexis
  • Poisoning, example arsenic
  • Radiation therapy
  • Rheumatoid arthritis
  • Sarcoidosis
  • Systemic lupus erythematosus (SLE)
  • Tuberculosis
  • Vitamin deficiencies

Other conditions not listed here may also cause or contribute to a low white blood cell count.

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