This policy brief describes key HIV viral load thresholds and the available viral load testing approaches for monitoring how well antiretroviral therapy is working for people living with HIV. It provides clarification for and elaborates upon the current treatment monitoring algorithm from the Consolidated guidelines on HIV prevention, testing, treatment, service delivery and monitoring: recommendations for a public health approach. This information can help people living with HIV to live healthy lives, ensure that HIV is not transmitted to other people and support policy-makers in determining the optimal allocation of resources for viral load testing and communicating the results.