Background <p>Community-based drug checking services have scaled up in response to the unregulated drug toxicity crisis across North America. We sought to assess the relationship between the detection of unexpected active drugs in a drug checking sample and subsequent engagement in risk reduction practices.</p> Methods <p>We used data from a cross-sectional study of people who used community-based drug checking services in British Columbia, Canada (March 2020–July 2024). We constructed multivariable logistic regression models to examine the relationship between the detection of unexpected active drugs (i.e., compounds that have psychoactive properties) in samples brought for analysis (using combination Fourier-transform infrared spectroscopy and immunoassay strips) and engagement in subsequent risk reduction practices (e.g., dose reduction, disposal of the drug).</p> Results <p>In total, 447 individuals were included: 174 (38.9%) reported detection of unexpected active drugs in their drug checking sample with the most common being benzodiazepines in expected opioid samples. The most common risk reduction behaviours were to dispose of the drug without using it (<i>n</i> = 24) and taking a smaller dose (<i>n</i> = 11). Through multivariable logistic regression, we found a positive association between detection of unexpected active drugs and engagement in risk reduction practices (adjusted odds ratio = 2.24; 95% confidence interval: 1.30–3.87).</p> Conclusion <p>Individuals who detected unexpected active drugs in their sample had higher odds of engaging in risk reduction practices. These findings highlight the potential of drug checking services as a harm reduction tool within a suite of services offered to combat the unpredictable and unregulated drug supply.</p>