Suppression of viral load, also known as HIV RNA, indicates that the virus is no longer replicating and infecting new cells. Viral load suppression has been shown to improve the health of people with HIV/AIDS-related illnesses and to reduce the risk of death due to AIDS.

The aim of antiretroviral therapy is to suppress HIV viral load as low as possible - ideally to an undetectable level using the most sensitive available tests. A widely available test can measure viral loads as low as 50 copies/ml (though some tests used for research purposes can detect even lower levels). Suppressing viral load below 50 copies/ml is now widely considered to be the goal of therapy both for people starting treatment for the first time and for treatment-experienced patients.

The evidence for a link between low viral load and a good prognosis among untreated people, and between viral load reduction and an improved prognosis in those receiving treatment, is discussed in Monitoring the Immune System, Uses of viral load testing.