Harm reduction measures employed by people using opioids with suspected fentanyl exposure in Boston, Baltimore, and Providence.

These data illustrate that PWUD employ a number of practices to reduce overdose risk in a context of unknown drug purity and content. Results may also guide efforts to identify early adopters of drug checking services and engage them in peer-outreach to target the most socially and structurally vulnerable PWUD, who are not reporting behavior change, with harm reduction messaging.