What Is a Dangerous White Blood Cell Count?

White blood cell counts that are too high or too low may be dangerous, depending on the cause. Infection can cause spikes, as well as blood cancers and other conditions.

White blood cells (leukocytes) make up about 1% of our blood and they help protect the body against illness and disease. 

White blood cells are produced in the bone marrow and stored in the blood and lymph tissues.

What Is the Function of White Blood Cells? 

There are several different types of white blood cells that each have slightly different functions. 

• Neutrophils
  • These white blood cells are the body’s first line of defense when infection occurs
  • They kill and digest bacteria and fungi and turn into pus when they die
  • These are the most numerous type of white blood cell, comprising about 60 to 70% of the total number of white blood cells
• Lymphocytes
  • These white blood cells create antibodies to fight against bacteria, viruses, and other harmful germs
  • There are many different types of lymphocytes
  • They make up about 30% of the total number of white blood cells
• Monocytes 
  • These white blood cells have a longer lifespan than other white blood cells and help to break down bacteria
  • They make up about 8% of the total number of white blood cells
• Eosinophils
  • These white blood cells attack and kill parasites and cancer cells
  • They also help with allergic responses
  • They make up about 1 to 3% of the total number of white blood cells
• Basophils
  • These white blood cells release histamine during an allergic reaction which promotes blood flow to the body’s tissues
  • They play a role in fighting infection
  • They make up about 0.5% of the total number of white blood cells

A normal white blood cell count is generally about 4,500 to 11,000/μL.

White blood cell counts that are too high or too low may be dangerous, depending on the cause. 

A high white blood cell count is called leukocytosis, which is generally diagnosed when white blood cell levels exceed 11,000/μL. This occurs when the immune system is stimulated in some way. 

Causes of high white blood cell counts include: 

• Infections, such as bacterial infections
• Leukemia and lymphoma, which are types of cancers
• Trauma 
• Extensive wounds or burns
• Acute or chronic inflammation such as from autoimmune disease, allergies, and other inflammatory problems
• Cigarette smoking
• Use of certain drugs, including corticosteroids heparin, lithium, albuterol, and similar drugs

A low white blood cell count is called leucopenia, which is generally diagnosed when white blood cell levels are below 4,500/μL. 

Causes of low white blood cell counts include:

• Tumors or disease in the bone marrow 
• Certain drugs, such as chemotherapy for cancer, some antibiotics and diuretics, anti-thyroid hormone drugs, captopril, seizure medications, and others
• Liver and spleen problems
• Radiation therapy to treat cancer
• Leukemia and other cancers
• Physical or emotional stress