What Does a Low White Blood Count Mean?

A slightly low white blood cell count is often nothing to worry about. However, a very low white blood count or one that persists can indicate medical problems.

If you’re not feeling well, are being monitored regularly for a health condition, or are simply having a physical, a visit to your doctor will likely include a complete blood count (CBC). This common lab test analyzes the number, shape, and size of blood cells, providing your doctor with information about whether your body has normal levels of healthy, oxygen carrying red blood cells and infection-fighting white blood cells (also known as leukocytes).

If your white blood cells are out of range, what does a low white blood count mean? Because white blood cells are a crucial part of your body’s immune system, having a low white blood cell count (also called a WBC count) can be an indication of a medical problem, ranging from minor to very serious.

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Understanding a low white blood count

White blood cells are measured in thousands per cubic milliliter (K/uL) of blood. So, a WBC count of 4.8 k/ul on a lab test indicates 4,800 white blood cells.

Normal ranges of white blood cells can vary slightly between men and women, the National Institutes of Health points out. On average, a normal white blood count is between 5,000 and 10,000 for men and 4,500 to 11,000 for women.

A CBC usually includes a differential count, sometimes referred to by doctors as a “diff.” This shows the percentage of different types of white blood cells in your blood and whether the cells appear normal under a microscope, the Leukemia and Lymphoma Society explains.

The five types of white blood cells and their normal range (measured in percentages) in blood are:

• Neutrophils (55% to 70%)
• Band neutrophils (0% to 3%)
• Lymphocytes (20% to 40%)
• Monocytes (2% to 8%)
• Eosinophils (1% to 4%)
• Basophils (0.5% to 1%)

A low white blood count has many causes

Leukopenia is a blanket term for having lower than normal white blood cells. And leukopenia can be caused by a host of health conditions, as well as by some treatments for medical problems.

Simply having a cold or the flu can cause a temporary low white blood count, but it will return to normal when your immune system is no longer revved up to fight the virus causing your illness. On the other hand, a low white blood count is associated with some serious viral infections, including malaria, hepatitis, and HIV.

Certain medications, including some antibiotics, can sometimes cause a low white blood count. Leukopenia may also be associated with genetic disorders that affect bone marrow. Even drinking alcohol to excess can lower your WBC count.

Along with a physical exam and other warranted tests, a differential, showing which white blood cell types are low, can help your doctor answer the question, “What does a low white blood count mean?”

One common type of leukopenia indicates you have a lower than normal level of neutrophils, the most common type of white blood cells. A healthy person usually has an absolute neutrophil count (ANC) between 2,500 and 6,000. When the ANC is below 1,000, it is called neutropenia.

While a lower-than-normal neutrophils count can be due to simple viral infections, it may also be a sign of more serious health problems. It can also indicate a medication you are taking should be changed or stopped (due to drug-induced neutropenia). Commonly prescribed drugs that can may cause neutropenia in some people include interferon, bupropion (Wellbutrin), steroids, and the anti-seizure medication lamotrigine (Lamictal). Neutropenia is often linked to autoimmune diseases such as lupus and rheumatoid arthritis, too.

Cancer treated with radiation and chemotherapy can result in neutropenia, the American Cancer Society explains. Your doctor will keep regular track of your white blood cell count and use your neutrophil count to check how well your immune system is working during cancer treatment. Your doctor will monitor your ANC closely because the risk of infection is much higher when neutrophils drop to below 500.

If your neutrophils are significantly low, you’ll be advised to take extra precautions to avoid getting an infection. Once treatment is over, your WBC count should head back toward more normal levels.

Bottom line? Don’t panic over a low WBC count!

Remember, nobody’s white blood count stays the same constantly; even a minor infection may lower the number of white bloods cells temporarily. What’s more, some people who are perfectly healthy have a slightly below average white blood count.

If your WBC count turns up as lower than normal, talk to your doctor. Don’t rely on figures you find on the internet as determining whether your white blood count indicates a health problem.

Other factors, such as age and race, may also affect normal ranges, according the National Heart, Lung and Blood Institute. And, if a WBC count is low due to an illness, it can return to normal after you recover.

So, don’t panic if you learn you have a low white blood cell count. Your doctor will use the finding, along with any symptoms you report and the result of other medical tests, if needed, to make a diagnosis and decide what treatment you may need.

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