White blood cells are part of your body's immune system defenses Overview of the Immune System The immune system is your body's defense system. It helps protect you from illness and infection. The immune system's job is to attack things that don’t belong in your body, including: Germs... read more against infection and cancer. Your body has several types of white blood cells White Blood Cells The main components of blood include Plasma Red blood cells White blood cells Platelets read more 
. Most white blood cells are made in your bone marrow.
What is a low white blood cell count?
A low white blood cell count is an unusually low number of one or more kinds of white blood cells.
A low white blood cell count puts you at increased risk of infection
Some infections can be life-threatening
A low white blood cell count can be a side effect of drugs, particularly chemotherapy drugs
Sometimes a low white blood cell count is caused by an infection or cancer
Doctors may do blood tests and bone marrow tests to see why your white blood cell count is low
Doctors may give you medicine to increase your white blood cells and antibiotics if you have a fever or other signs of infection
What causes a low white blood cell count?
There are many causes of a low white blood cell count:
Infections: HIV Human Immunodeficiency Virus (HIV) Infection and AIDS The human immunodeficiency virus (HIV) is a type of virus called a retrovirus. It causes AIDS (acquired immunodeficiency syndrome), which is life-threatening. HIV is called an immunodeficiency... read more , many other viral infections, and severe bodywide bacterial infection ( sepsis Sepsis Sepsis is when germs (bacteria) get into your bloodstream and trigger a serious body-wide reaction. When sepsis is severe, one or more of your organs may shut down. For example, your kidneys... read more )
Cancer that starts in the bone marrow, such as leukemia Overview of Leukemia Leukemias are cancers of white blood cells or of cells that develop into white blood cells. White blood cells develop from stem cells in the bone marrow. Sometimes the development goes awry... read more , lymphoma Overview of Lymphoma Lymphomas are cancers of lymphocytes, which reside in the lymphatic system and in blood-forming organs. Lymphomas are cancers of a specific type of white blood cells known as lymphocytes. These... read more
, and myeloma Multiple Myeloma You have several types of blood cells: Red blood cells carry oxygen White blood cells fight infection Platelets help your blood clot when you're bleeding Plasma cells are a special type of white... read more Metastatic cancer in the bone marrow, such as from breast cancer Breast Cancer Cancer is when cells grow abnormally. Cancer cells don't look or work like normal cells and keep multiplying out of control. Cancer cells can invade and destroy nearby healthy tissue. Sometimes... read more or prostate cancer Prostate Cancer Cancer is the out-of-control growth of cells in your body. Cells are the tiny building blocks of your body. Cells specialize in what they do. Different organs are made of different kinds of... read more
Other bone marrow problems, such as myelodysplastic disorders
What are the symptoms of a low white blood cell count?
A low white blood cell count has no specific symptoms. You get symptoms because you develop frequent infections. Sometimes the infections are unusual ones that most people don't get.
Symptoms of infections can start suddenly or slowly and can include:
Fever
Rash
Painful sores in your mouth and anus (the opening at the end of the digestive tract where stool comes out)
How can doctors tell if my white blood cell count is low?
Doctors can tell you have a low white blood cell count by doing a routine complete blood count (CBC). If you're getting treatments or have a disease that can lower your white blood cell count, doctors check your CBC often.
Sometimes, the cause is obvious, such as if you’re getting chemotherapy or radiation therapy for cancer.
If the cause isn't clear, doctors may do:
Blood, urine, and imaging tests looking for infection
Bone marrow biopsy (removing some bone marrow with a needle to do tests on it)
How do doctors treat a low white blood cell count?
Doctors treat a low white blood cell count using:
Antibiotics to treat any infections
Medicines to push your body to make more white blood cells
Treatment for any diseases that may be causing the count to be low
