Non–prescribed buprenorphine preceding treatment intake and clinical outcomes for opioid use disorder

•Rates of non-prescribed buprenorphine use preceding treatment entry have increased and may be a pathway to entering treatment.•Over half of patients were buprenorphine positive at intake, largely reflecting street access rather than prescription use.•Patients using non-prescribed buprenorphine had double the retention and half the rate of opioid use while in care.•Care navigation and other supports may be beneficial for patients identified as buprenorphine negative at treatment entry.