Low White Blood Cell Count

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Introduction

What is a low white blood cell count?

A low white blood cell (WBC) count is a decreased number of white blood cells (leukocytes) in the blood. A low WBC count is referred to medically as leukopenia.

WBCs, which are produced in the bone marrow, are an important part of your immune system and your body’s natural weapon to fight off bacteria, viruses and other germs. When you have a low white blood cell count you may be immunosuppressed, which means that you are more vulnerable to potentially serious infections that do not go away or are hard to treat.

A low WBC count is usually discovered by your physician or health care provider during routine testing or through the course of diagnosis and treatment for an underlying disease, disorder or condition. A normal WBC count is approximately 4,500 to 10,000 WBCs per microliter of blood. A low WBC count is generally below 3,500 WBCs per microliter of blood, but this number varies depending on the medical laboratory, the particular test used, and the individual medical practice.

The significance of a low WBC count varies and may be more (or less) serious depending on your medical history, overall health, and the underlying disease, disorder or condition. Some people may naturally have a mildly low WBC count. The normal range of low to high WBC counts also varies by age and gender.

A low WBC count is often linked to problems with the bone marrow and the inability to make enough white blood cells. Autoimmune diseases that attack your white blood cells can also lead to a low WBC count. Several different prescribed drugs, including chemotherapy, are known to decrease WBC production or destroy WBCs.

A low WBC count can be serious because it increases your risk of developing a potentially life-threatening infection.  If you have a low WBC count, you will probably be advised by your medical professional to avoid situations that expose you to infectious and contagious diseases. Seek prompt medical care if you have a low WBC count and have signs of an infection, such as a fever, swollen lymph nodes, sore throat, or skin lesions.

Symptoms

What other symptoms might occur with a low white blood cell count?

A low WBC count may be accompanied by other symptoms, which vary depending on the underlying disease, disorder or condition. Symptoms can include:

Symptoms that might indicate a serious condition

A low WBC count can be serious because it increases your risk of developing a potentially life-threatening infection. Seek prompt medical care if you have a low WBC count and have signs of an infection, such as a fever, swollen lymph nodes, sore throat, or skin lesions.

Causes

What causes a low white blood cell count?

A low WBC count can be caused by a variety of diseases, disorders and conditions, as well as certain medications. In some cases a cause cannot be found.

Diseases and disorders that can cause a low white blood cell count

A low WBC count can be due to a variety of different conditions that either destroy WBCs or inhibit their production in the bone marrow. These include:

Medications that can reduce the number of white blood cells

A low WBC count can also be caused by medications or medical treatments that you are receiving for an underlying disease, disorder or condition, such as:

  • Antibiotics

  • Anticonvulsants

  • Antihistamines

  • Antithyroid drugs

  • Arsenic

  • Barbiturates

  • Chemotherapy drugs

  • Diuretics (“water pills”)

  • Radiation therapy

  • Sulfonamides

What are the potential complications of a low white blood cell count?

A poorly controlled or untreated low WBC count can be serious and even life threatening due to increased vulnerability to potentially life-threatening infectious diseases, such as:

Life-threatening complications of these diseases include:

  • Organ failure

  • Recurrent and resistant infections that are difficult to treat

  • Septic shock

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Nov 18
  1. WBC count. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/003643.htm
  2. What is Aplastic Anemia? National Heart Lung and Blood Institute Diseases and Conditions Index. National Institutes of Health. http://www.nhlbi.nih.gov/health/dci/Diseases/aplastic/aplastic_whatis.html
  3. Explore Blood Tests. National Heart Lung and Blood Institute Diseases and Conditions Index. National Institutes of Health. http://www.nhlbi.nih.gov/health/dci/Diseases/bdt/bdt_types.html
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