Low White Blood Cell Count (Leukopenia): Causes, Tests and When to Be Seen

What it involves

MedlinePlus explains that a white blood count measures the number of white blood cells in your blood. These cells, also called leukocytes, are part of the immune system and help the body fight infections and other diseases. A low count is called leukopenia, and the test cannot confirm a diagnosis by itself.

Who this is for

• Adults whose blood work showed a white blood cell count below the lab's reference range.
• Patients with repeated infections, fevers or wounds that are slow to heal.
• People taking medicines, including chemotherapy, that can lower blood counts.
• Anyone with an autoimmune or liver condition who needs their blood counts followed.

What to expect

• Questions about infections, fevers, medicines, past illnesses and family history
• An exam that includes checking lymph nodes, the belly and the skin
• Repeat blood work, which the practice offers, often with a blood differential
• A referral to a blood specialist for a blood smear or bone marrow test when it is needed

What the number is measuring

A white blood count measures the total number of white blood cells, and MedlinePlus lists five major types: neutrophils, lymphocytes, monocytes, eosinophils and basophils. Neutrophils mostly target bacterial infections and lymphocytes mostly target viral infections. A separate test called a blood differential shows how much of each type you have. The complete blood count guide explains where the white count sits on a standard blood report and how to read the other lines next to it.

Causes MedlinePlus lists

For a low count, MedlinePlus names bone marrow damage from infection, disease or treatments such as chemotherapy, cancers that affect the bone marrow, an autoimmune disorder such as lupus, and HIV. It also lists lymphoma and diseases of the liver or spleen among the disorders linked to a low count. Certain medicines can lower the number of white cells too, which is why your provider reviews everything you take. The lupus guide and the cirrhosis guide describe two of the conditions on that list.

Symptoms that make the test more urgent

The test is used when there are signs of infection, inflammation or an autoimmune disease. MedlinePlus lists fever, chills, body aches, headache, a wound that is red with pus or will not heal, and an ongoing cough as signs of infection. If you have a weak immune system or take a medicine that lowers your immune response, your provider may check the count more often and adjust treatment if it gets too low. The fever in adults guide explains when a fever needs a same-day call.

What happens at the visit

Your provider reviews your medicines, recent infections and symptoms, examines your lymph nodes and belly, and usually repeats the blood count, because a single low result can be a one-time change. MedlinePlus says the count is often compared with a blood differential, and that a complete blood count, a blood smear or a bone marrow test may follow to confirm a cause. The practice offers blood work. A blood smear review or a bone marrow test is done by referral to a blood specialist.

Getting the blood test done

MedlinePlus says no special preparation is needed for a white blood count, though you may need to stop some medicines before the test, so tell your provider about everything you take and do not stop any on your own. A health care professional takes a blood sample from a vein in your arm with a small needle, and you may feel a sting. The fasting blood work preparation guide explains when a blood draw does need fasting, which this one does not.

When to call and when to go to the ER

Call the office the same day for a fever, chills, a wound that looks infected or repeated infections with a known low count. Go to the ER or call 911 for a high fever with shaking chills, confusion, a racing heart, trouble breathing or fainting, which can be signs of a serious infection. The sepsis warning signs guide lists those signs. Swollen glands that keep growing are covered in the swollen lymph nodes guide.

Sources

• MedlinePlus Medical Test: White Blood Count (WBC)