Viral Load Measurement
A viral load test measures how much
human immunodeficiency virus (HIV) is in the blood.
The results can take up to 2 weeks.
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab and depend upon which testing method is used (RT-PCR, bDNA, NASBA). Your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
load results are reported as the number of HIV copies in a
milliliter (copies/mL) of blood. Each virus is called
a "copy," because HIV reproduces by making copies of itself
HIV is not detected in the
HIV is detected in the blood.
Your doctor will compare your current measurement with previous
If your viral load increases, it means the infection is
getting worse. If the viral load drops, it means that the infection is being
What Affects the Test
Reasons you may not be able to
have the test or why the results may not be helpful include:
- Having another
infection, such as
- Having gotten a recent vaccine, such as a flu vaccine.
What To Think About
- The results from the different methods (RT-PCR,
bDNA, NASBA) to measure viral load are not interchangeable. This makes it
important to use the same method of measuring each time.
undetectable viral load result does not mean that you no longer have HIV in
your blood. It simply means that the amount of HIV in the blood was too low for
the test to detect. HIV still can be passed to another person even when the
viral load cannot be detected.
- The viral load test is not used
routinely to diagnose HIV. The HIV antibody test is used for this purpose. To learn more, see the topic
Human Immunodeficiency Virus (HIV) Test.
- The viral load test is more accurate than a CD4+ count
to evaluate the activity of HIV. The CD4+ count measures how well your
immune system is working and may be used to determine
when to start
antiretroviral therapy. The viral load test is used to
determine the response to antiretroviral therapy. No HIV should be detected in the blood of people whose treatment is successful. To learn more about
the CD4+ count, see the topic