The clinical knowledge that people living with HIV who maintain an undetectable viral load and therefore cannot transmit HIV sexually, known as Undetectable equals Untransmittable (U=U), has reached a critical mass of adults, but it is relatively silenced within adolescent HIV care and support. We argue that understanding the full range of opportunities enabled by viral suppression, including the elimination of transmission risk, could transform adolescents' understanding of living with HIV, incentivise optimal treatment engagement and support and sustain their positive mental health. However, the reluctance to discuss U=U with adolescents means that we are not providing them with adequate access to the information and tools that would help them to succeed. We need to recognise, value, and invest in the mediating role of building viral load literacy, illustrated by conveying U=U in ways that are meaningful for adolescents, to accelerate viral suppression. Rather than protect, rationing access to information on U=U only increases their vulnerability and risk to poor HIV and mental health outcomes.