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Types of Lab Tests

Lab types and why they are important

Once you have tested positive for HIV, your HIV care provider will probably ask you to take a number of laboratory tests. The list may include:

  • CD4/T-cell count: A count of your CD4 cells gives a general measure of the health of your immune system, and is a good measurement of immunosuppression. A normal CD4 cell count is more than 500 cells per cubic millimeter (mm3) of blood. If you have a CD4 count of fewer than 200/mm3, you will be diagnosed as having AIDS.
    Why it’s important: This is a good measure of your risk of opportunistic infections and the strength of your immune system. It will give you and your healthcare provider the information you need to decide the best way to treat your HIV disease.
  • CD4 Percentage: This measures how many of your white blood cells are actually CD4 cells. This measurement is more stable than CD4 counts over a long period of time, but, for most people, the CD4 count remains a more reliable measure of immune function than CD4 percentage.
    Why it’s important: This measurement is less likelyto vary in between blood tests than CD4 counts (which can vary from month to month or day to day).
  • Viral Load (VL): This test measures the amount of HIV in your blood.
    Why it’s important: The goals of HIV treatment are to keep your viral load at undetectable levels and to keep your CD4 count high. A viral load test offers a good indicator of how well your treatment is working to achieve those goals.
  • Complete Blood Count (CBC): This is a measure of the concentration of red blood cells, white blood cells, and platelets in a sample of your blood.
    Why it’s important: A CBC is one of the most commonly ordered blood tests. It can reveal infections, anemia (abnormality in your red blood cells), and other medical issues.
  • Serum Chemistry Panel: This test helps provide information about your body's metabolism. It gives your doctor information about how your kidneys and liver are working, and can be used to evaluate your blood sugar levels, calcium levels, etc.
    Why it’s important: Some HIV medications can have serious side effects, and this test helps your healthcare provider to monitor the impact of your medications on your body’s ability to function normally.
  • Sexually Transmitted Disease (STD) Screening: These screening tests check for syphilis, gonorrhea and chlamydia.
    Why it’s important: Having an STD, can make it easier to pass HIV to others. Untreated STDs can also be damaging to your own immune system.
  • PAP Smear (Cervical and Anal): This is a screening test for abnormal cells that could become cancerous. It involves using a swab to take cell samples directly from the cervix and anus.
    Why it’s important: For women living with HIV, abnormal cell growth in the cervix is common, and abnormal anal cells are common for both men and women who are HIV-positive. These abnormal cells may become cancerous if they aren’t treated.
  • Hepatitis A, B, and C tests: These blood tests check for current or past infection with Hepatitis A, B, or C...
    Why it’s important: Some people who are living with HIV are also coinfected with hepatitis. Checking you for hepatitis A, B, and C can help your provider to determine if you need to be treated, or if you are a candidate for one of the existing hepatitis vaccines.
  • Tuberculosis (TB) Skin Test: This skin test checks for exposure to TB. A positive skin test does not mean you have active TB, but it means you will need further evaluation and possible treatment.
    Why it’s important: Untreated TB can be a deadly disease for people living with HIV. Early screening and treatment will help limit your risk of severe illness, as well as lower your chances of transmitting TB to others if you do have it.
  • Toxoplasmosis Screening: This test checks for exposure to a parasite that can cause severe damage to the brain, eyes, and other organs in people with weakened immune systems.
    Why it’s important: Toxoplasmosis can be a deadly opportunistic infection for people living with HIV. Your clinician needs to know if you have been exposed to the parasite that causes toxoplasmosis or are at risk for exposure. This will help your healthcare provider to decide if you need preventative treatment. If your CD4 count falls below 100/mm3, you will probably need to do another screening, even if your earlier screens were negative.
  • Fasting Lipid Panel (Cholesterol and Triglycerides): These tests measure your total cholesterol level, as well as give you information about the different types of fat proteins in your body.
    Why it’s important: Some HIV medications can affect your cholesterol levels and the way your body processes and stores fat. This can make you prone to other medical problems, including heart problems.
  • Fasting Glucose (blood sugar): This test measures your blood sugar levels to check for signs of pre-diabetes or diabetes.
    Why it’s important: Some HIV medications can affect blood sugar levels, potentially leading to complications like diabetes.

Fact Sheets & Print Materials

Related Topics on AIDS.gov

Frequently Asked Questions

How often will my provider check my CD4 count and viral load?

Your provider will probably check your CD4 count at your first visit. Then—depending on what your counts are and whether you both decide it’s time to begin treatment—you can usually expect to undergo viral load testing every 3-6 months. Typically, once you are on a good medication regimen, have an undetectable viral load, and have an increasing CD4 count, you will take a viral load test every 6 months.

Why does my provider want to order so many tests?

It’s important to remember that your provider will be treating your HIV but also needs to consider your overall health and well-being. These tests, along with the information you provide and your physical exam, all help your provider to develop the best plan of care to help you lead a healthy life.

Additional Resources

Last revised: 10/11/2010