White blood cells, also called leukocytes, fight infection. They move throughout your body in your blood, looking for invaders. And your body is continuously making a fresh supply. Your doctor measures how many of these
cells you have by sending some of your blood to a lab to do a complete blood count, or CBC. Your white blood cell count is one of the numbers you get back from this test. It may point toward or confirm a diagnosis, or show whether a treatment is working or not. Most often, a low white blood cell count is nothing to worry about. How many white blood cells (WBCs) someone has varies, but the normal range is usually
between 4,000 and 11,000 per microliter of blood. A blood test that shows a WBC count of less than 4,000 per microliter (some labs say less than 4,500) could mean your body may not be able to fight infection the way it should. A low number is sometimes called leukopenia. Your doctor will do a physical
exam and consider symptoms that you have along with your past medical issues to figure out what's behind your result. Bone marrow problems: The spongy center of your bones, which is called the bone marrow, makes blood cells. Low WBC counts are often linked to bone marrow problems. Being around certain chemicals, like benzene and pesticides, as well as some types of cancer and
cancer treatments including chemotherapy and radiation, can hurt your bone marrow's ability to make WBCs. Autoimmune disorders: Some
autoimmune diseases, like lupus and rheumatoid arthritis, will tell your body to attack and destroy its own WBCs. Infection: Viruses can affect your bone
marrow and cause low WBCs for a while. Severe infections, like blood infections, can lead to your body using up WBCs faster than it can make them. HIV //www.webmd.com/hiv-aids/understanding-aids-hiv-symptoms kills a specific kind of white blood cell. Medicines: Some
drugs, including antibiotics, can destroy WBCs. Nutrition: Not eating well or low levels of certain
vitamins, such as folic acid and B12, can affect how your body makes WBCs. Alcohol abuse can mess with the nutrients in
your body and with WBC counts, too. Spleen problems: The spleen also makes WBCs. Infections, blood clots, and other problems can make it swell and not work the way it should. This will drop your WBC count. Why Is My White Blood Cell Count Low?
What Is "Low"?
Causes
If there's no clear reason for a low white blood cell count, your doctor will probably want to do the test again, or do a differential or "diff" along with the CBC. This other test gives a lot more detail. There are normal ranges for each of the five kinds of WBCs, and some problems only affect one type. The results of a diff could help your doctor narrow down what's going on. Many times, a repeated test will show that your WBC
count is normal. Your doctor may want to do more tests, based on the symptoms you have. For instance, you might get checked for strep throat or mono. Other blood tests can look for a
viral infection, inflammation, or allergies. The doctor may want to take a sample of your
bone marrow to see if it's healthy. When your WBC count is very low, you may need to take steps to avoid an infection. Your doctor may ask you to see a hematologist. This is a specialist who has extra training for diagnosing and treating blood count problems. If your WBC count
stays low or keeps getting lower, work with your doctor to find out why it's happening. The right treatment should help your white blood cell count return to normal.Follow-up Tests
What Happens Next?
Blood cell counts give your doctor important clues about the state of your health before, during and after treatment. Blood counts alone can't determine whether you have a blood cancer, but they can alert your doctor if further testing is needed. A complete blood count (CBC) is the number and types of cells circulating in your
blood. Your CBC is measured using laboratory tests that require a small blood sample. Blood is composed of several types of cells:
- Red cells, sometimes referred to as erythrocytes, pick up oxygen as blood passes through the lungs and release it to the cells in the body.
- White cells, sometimes referred to as leukocytes, help fight bacteria and viruses.
- Platelets help your blood clot in response to a cut or a wound.
A CBC also tests hemoglobin and hematocrit:
- Hemoglobin is a protein used by red cells to distribute oxygen to other tissues and cells in the body.
- Hematocrit refers to the amount of your blood that's occupied by red cells.
Normal Blood Counts
Normal blood counts fall within a range established by testing healthy men and women of all ages. The cell counts are compared to those of healthy individuals of similar age and sex. Nearly all lab reports include a "normal" range or high and low "values" to help you understand test results.
Normal Ranges of Blood Cell Counts for Healthy Adults and Children
| Men | 4.7 to 6.1 million | 5,000 to 10,000 | 150,000 to 400,000 | 42 to 52 | 14 to 18 |
| Women2 | 4.2 to 5.4 million | 4,500 to 11,000 | 150,000 to 400,000 | 37 to 47 | 12 to 16 |
| Children3 | 4.0 to 5.5 million | 5,000 to 10,000 | 150,000 to 400,000 | 32 to 44 | 9.5 to 15.5 |
1The ratio of hematocrit to hemoglobin is about 3 to 1.
2Normal ranges for women who are pregnant differ from these ranges.
3These ranges are for children from infancy to adolescence; speak with your doctor to find out specific values for infants and young children.
White Cell Differential
Differential count, sometimes referred to as a "diff," is a breakdown of the different types of white cells. A white cell (WBC) differential also checks whether white cells appear normal. The five types of white cells and the approximate percentage they make up in the 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%)
Until children are more than 4 years old, they have a higher percentage of lymphocytes in their blood than adults do.
How Blood Cancers Affect Blood Counts
Blood cancers can affect blood cell counts in a number of ways, either lowering or increasing measurements. If you're currently receiving cancer treatment such as chemotherapy, drug therapy or radiation, your blood counts will be affected. Blood counts usually return to normal after treatment is complete.
Should You Keep Track of Your Blood Counts?
Some people want to know the results of their blood count tests so they can take preventive measures to protect their health or to what's causing their symptoms. For example:
- If you have anemia as a result of low red cell counts, you'll understand why you have low energy levels or are unable to carry out everyday tasks.
- If you have low white cell counts and develop a fever, you'll know to contact your doctor promptly.
- If your platelet counts are too low, you can bleed or bruise easily, so you may choose to avoid activities that have a risk of injury.
Noncancerous Conditions
About 5 percent of healthy people will have test results outside of the "normal" range. If one or more of your blood cell counts is higher or lower than normal, your doctor will try to find out why. Many noncancerous conditions can contribute to low or high blood cell counts, such as those in the table below.
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