The research team will enroll 100 young adults who use cocaine, heroin, inject drugs, or purchase prescription medications on the illicit market in a pilot study to be known as the Rhode Island Young Adult Prescription and Illicit Drug Study (RAPIDS). Participants will be trained to use a take-home home rapid drug test to test for the presence or absence of fentanyl in their drug supply. Half of the enrolled participants will be asked to test their urine for presence or absence of fentanyl, and the other half will be asked to test their drug residue for presence or absence of fentanyl. All participants will receive up to 15 take-home rapid drug tests for fentanyl. A follow-up survey will examine and compare utilization of the tests between the two groups. The study will be guided by the information-motivation-behavioral skills (IMB) model of engagement in health behaviors. The IMB model hypothesizes that if a person possesses the information, motivation, and behavioral skills to act, there is an increased likelihood that she/he will fulfill and maintain the desired behaviors (behaviors that will reduce accidental overdose).