Findings from 35 qualitative interviews with drug users who were engaging in or who had engaged in sex work in Dublin, Ireland, illuminated how, because of a result of felt stigma and internalized shame, they tried to hide their drug use, thus endangering their own lives. This group carried multiple layers of stigma because of sex work, drug use (including injecting drug use), and having contracted human immunodeficiency virus (HIV) or hepatitis C virus (HCV). This stigma was powerfully reinforced by the language routinely used by health professionals. To improve the effectiveness of harm reduction interventions, it is recommended that service providers change their language, in particular in recognition of the human dignity of these clients, but also to help attract and retain drug users in services, and to help reduce the unacceptable mortality levels among drug users.