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A T cell count is a blood test that measures the number of T cells in your body. A T cell is a type of white blood cell. White blood cells are also called lymphocytes. These cells fight off diseases. The two categories of lymphocytes are T cells and B cells. The T cells respond to viral infections, while the B cells fight bacterial infections. Your body sometimes has too many or too few T cells. This may be a sign that your immune system isn’t functioning properly.
A T cell count may also be known as a thymus-derived lymphocyte count, or a T lymphocyte count.
If you’re being treated for HIV, this test may be known as a CD4 cell count. Some T cells contain a CD4 receptor. This receptor is where HIV attaches to the T cell. When the number of CD4 T cells drops below a certain point, it may be time for you to begin treatment for HIV and AIDS.
Your doctor may order a T cell count if you’re having symptoms of an immunodeficiency disorder, such as HIV, or other conditions, such as cancer or leukemia.
The symptoms of an immunodeficiency disorder include:
A low T cell count is more common than a high T cell count. Low T cell counts usually indicate problems with your immune system or lymph nodes. Low T cell counts may be due to:
Less often, you might have a T cell count that’s higher than normal. A high T cell count can be due to:
A T cell count requires only a small sample of your blood. There’s little you need to do to prepare for it.
Be sure to tell your doctor about all the medications you’re taking, including any over-the-counter and prescription medications or herbal supplements, before your test. Certain medications can impact your T cell count, which will alter the results of your test. Your doctor may ask you to stop taking your medications for a little while, or they may change the dosage before your test.
Medications that may affect your T cell count include:
Recent surgery or highly stressful experiences can also affect your T cell count. You should tell your doctor if any of these situations apply to you.
Remember, your doctor only needs a small sample of your blood to get a T cell count. This procedure is also known as a blood draw or venipuncture. You may have the test in a medical laboratory or a doctor’s office.
You’ll be free to go about your day following the blood draw. Your sample will go to a laboratory, where technicians will count the number and type of white blood cells present.
There are very few risks associated with a T cell count. However, people with compromised immune systems often have this test. They may be at greater risk for developing an infection than the rest of the population.
Other possible risks of a T cell test include:
According to the U.S. Department of Health and Human Services, your T cell count should be between 500 and 1,200 T cells per cubic millimeter of blood.
Your doctor will discuss any further tests you need for a diagnosis. They’ll also provide you with treatment options if your results are above or below this range.
Written by: Janelle Martel
Medically reviewed on: Dec 14, 2015: Steven Kim, MD
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