Key takeaways
- A T cell count is a blood test that measures the number of T cells, a type of white blood cell crucial for fighting off diseases, especially viral infections.
- This test helps identify issues with the immune system or lymph nodes, indicated by T cell counts outside the typical range of 500 to 1,500 cells per cubic millimeter of blood.
- Factors such as certain medications, recent surgery, and significant stress can influence T cell count results, so it’s important to discuss these with your doctor before the test.
A T cell count is a blood test that measures the number of T cells in the body. T cells are a type of white blood cell 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 the immune function of other cells, while the B cells fight bacterial infections.
The body sometimes has too many or too few T cells. This may be a sign that the 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.
Read on to learn more about T cell counts, including why you might need the blood test, how to prepare, and more.
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, such as immunosuppressants, 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. It’s important to keep taking your medication as usual unless your doctor instructs otherwise.
Some medications that may affect your T cell count include:
Recent surgery or highly stressful experiences can also affect your T cell count. It’s important to let a healthcare professional know if any of these situations apply to you.
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.
The appointment takes around 10 minutes. Giving a blood sample typically happens as follows:
- A healthcare professional will begin by cleaning an area of skin on your arm or hand with an antiseptic to help prevent infection.
- They may tie a tourniquet or band around your upper arm so that blood collects in your vein.
- 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.
- You may feel some pain or discomfort while having your blood drawn. This usually feels like a pricking or stinging sensation. You can help ease this pain by relaxing your arm.
- When the healthcare professional finishes drawing blood, they’ll remove the needle and the tourniquet and apply a bandage to the puncture wound. You can apply pressure to the wound to stop bleeding and help 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 blood test. Blood tests are generally safe.
Other possible side effects of blood tests include:
- bruising
- multiple puncture wounds if the technician has trouble finding a vein
- excessive bleeding
- lightheadedness or fainting
- hematoma, which is a collection of blood under the skin
- an infection at the puncture site
Speak with a healthcare professional if you have any concerns about the possible risks or side effects of blood tests.
A typical T cell count should be between
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:
- viral infections, such as influenza
- aging
- immunodeficiency disorders
- exposure to radiation
- HIV and AIDS
- cancers that affect the blood or lymph nodes, such as Waldenstrom’s macroglobulinemia, leukemia, and Hodgkin’s disease
- congenital T cell deficiency, in some rare cases
High T cell count
Less often, you might have a T cell count that’s higher than usual. A high T cell count can be due to:
- infectious mononucleosis, also known as mono or “the kissing disease”
- acute lymphocytic leukemia (ALL), a type of cancer that affects the white blood cells
- multiple myeloma, a type of cancer that affects the plasma cells in bone marrow
- genetic disorders, such as in autoimmune lymphoproliferative syndrome
Depending on the results of the T cell count, your doctor will discuss any further tests you need after your blood test. They’ll also provide you with treatment options if your results are above or below this range.
A T cell count measures the number of T cells in your blood. The blood test can help determine if there are issues with your immune system or lymph nodes.
Some factors, such as medications, surgery, and stress, can affect your T cell count. It’s best to speak with the healthcare professional performing the blood test about any of these factors before they do the test.
A low or high T cell count can indicate an underlying health condition. For example, low T cells can suggest a viral infection, HIV, or cancer. A high T cell count can be due to conditions such as acute lymphocytic leukemia (ALL) or multiple myeloma.
Once your doctor receives your test results, they may order further testing to help determine the cause of a low or high T cell count, where necessary. They can also advise on any treatments that may help manage your T cell count and treat any underlying cause.