BACKGROUND AND AIMS: The evolving landscape of illicit drug markets necessitates effective approaches to harm reduction and addiction prevention for people who use drugs (PWUD). In response, integrated drug checking services (DCS), which combine chemical analyses and psychosocial interventions, have been shown to contribute to safer drug use behaviour, particularly in festival settings. However, little is known about how people who predominantly use drugs occasionally engage with and perceive fixed-site DCS and how specific service characteristics contribute to its overall impact. In this study, we qualitatively assess the impact of a well-established multimodal DCS in Vienna, Austria, from the viewpoint of actual and prospective users.

METHODOLOGY: From June 2024 through January 2025, semi-structured interviews were conducted with 23 PWUD (7 self-identified as female; 16 as male), of whom 12 were current users of at least one drug checking modality (mobile or fixed-site), and 11 had no prior experience with DCS. Including both groups provided a broader perspective, acknowledging the limited reach of the DCS and the access barriers faced by some individuals. Participants reported diverse drug use patterns, with many reporting occasional use. Interviews were analysed using reflexive thematic analysis.

RESULTS: During analysis, three central themes were developed: (1) "Knowledge creates safety and agency" illustrates how knowledge of the exact composition of a substance fosters a sense of safety and empowers individuals to make informed decisions about their drug use; (2) "Personal circumstances as key to engagement and impact" captures the effect of situational context and current needs in shaping the depth and engagement with DCS; and (3) "Social effects beyond the individual" reflects the broader impact of drug checking, on the level of peers, people who sell drugs, and the drug market.

CONCLUSION: Our findings suggest that DCS can considerably promote safer use behaviour, as well as risk awareness and management among PWUD. To be effective as a tool for early intervention and addiction prevention, services must remain low threshold to address the diverse needs of PWUD, allowing for varying degrees of engagement, such as keeping psychosocial counselling optional. Acknowledging the critical role of peers in building trust, facilitating access, and sharing safer use information underscores the importance of social relations in extending the harm reduction impacts of DCS.