A white blood cell (WBC) count outside the normal range (generally 4,500–11,000/μL) can be alarming, depending on the cause and the extent of the deviation.
High White Blood Cell Count (Leukocytosis)
A high WBC count, exceeding 11,000/μL, is considered leukocytosis. While not inherently dangerous, it signals the body's response to an underlying condition. Several factors can cause this, including:
- Infections: Bacterial, viral, or fungal infections trigger an increase in WBCs to fight the invaders.
- Inflammation: Conditions like arthritis or autoimmune diseases can cause elevated WBC counts.
- Injury: Trauma or tissue damage also prompts a rise in WBCs.
- Blood cancers: Leukemias and lymphomas can significantly elevate WBC levels.
A very high WBC count, such as above 20,000/µL, warrants immediate medical attention as this strongly suggests a serious underlying condition like a severe infection or blood cancer. The specific type of elevated white blood cell is crucial for diagnosis, so a full blood count (CBC) with differential is necessary.
Low White Blood Cell Count (Leukopenia)
A low WBC count, generally below 4,000/μL (though the threshold may vary slightly depending on the lab and individual), is considered leukopenia. This indicates the body's reduced ability to fight infections, potentially leading to severe consequences. Causes can include:
- Bone marrow disorders: Conditions affecting bone marrow function, where WBCs are produced, can drastically reduce their number.
- Autoimmune diseases: Certain autoimmune diseases can attack and destroy WBCs.
- Medications: Some medications, like chemotherapy, can suppress bone marrow function and decrease WBC counts.
- Viral infections: Some viruses, like HIV, can deplete WBC numbers.
A severely low WBC count severely compromises the immune system, making infections much more dangerous. Medical attention is crucial for individuals with leukopenia.
It's crucial to remember that a single WBC count is not enough for diagnosis. A complete blood count (CBC) along with a differential count (identifying the proportion of different types of WBCs) and a thorough medical history are necessary to determine the cause of an abnormal WBC count and appropriate treatment.
