What is the definition of an undetectable HIV viral load?

• A. <20 copies/mL
• B. <50 copies/mL
• C. Undetectable by the assay (commonly <50 copies/mL)
• D. 0 copies/mL

Answer: (C)

Undetectable means the HIV RNA amount is below the test’s ability to measure it. In most standard tests, this threshold is around 50 copies/mL, so a viral load reported as undetectable means it’s below that limit. Importantly, this does not guarantee zero copies in the body—some virus may be present below the assay’s detection limit, and newer, more sensitive tests can detect lower levels (e.g., around 20 copies/mL). The key idea is that “undetectable” is defined by the test’s limit of detection, not by a fixed fixed number.