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 (WBC). WBCs 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 and boost immune function of other cells, 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.

Your doctor may order a T cell count if you’re having symptoms of an immunodeficiency disorder, such as HIV. Symptoms associated with other conditions, such as leukemia or other cancers, may also prompt a T cell count.

The symptoms of an immunodeficiency disorder include:

  • frequently recurring infections
  • severe infections from bacteria or other organisms that don’t usually cause severe infections
  • trouble recovering from illnesses
  • infections that don’t respond to treatments
  • recurring fungal infections, such as yeast infections
  • recurring parasitic infections

A T cell count requires only a small sample of your blood. There’s little you need to do to prepare for it.

Before your test, be sure to tell your doctor about all the medications you’re taking. This includes any over-the-counter (OTC) and prescription medications or herbal supplements.

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.

  1. A healthcare provider will begin by cleaning an area of skin on your arm or hand with antiseptic to help prevent infection.
  2. They’ll tie an elastic band around your upper arm so that blood collects in your vein.
  3. Next, they’ll insert a sterile needle into your vein and draw blood into a tube. The amount of blood drawn depends on the number of tests that your doctor ordered. It should take no longer than a couple of minutes to collect the blood sample needed.
  4. You may feel some pain while having your blood drawn. This usually feels like a pricking or stinging sensation. You can help ease this pain by relaxing your arm.
  5. When the technician finishes drawing blood, they’ll remove the elastic band and the needle and apply a bandage to the puncture wound. You should apply pressure to the wound to stop bleeding and prevent bruising.

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 HIV.gov, a healthy T cell count should be between 500 and 1,600 T cells per cubic millimeter of blood (cells/mm3).

Low T cell count

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:

High T cell count

Less often, you might have a T cell count that’s higher than normal. A high T cell count can be due to:

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.

Medications may be prescribed to increase your T cell count. No specific foods have been shown to increase the number of WBCs or T cells in the body. However, a healthy diet can help to boost the immune system overall.