Fentanyl rarely shows up labeled as what it is. It gets pressed into counterfeit pills made to look like Xanax or oxycodone, and it gets mixed into heroin, cocaine, and other street drugs, so people take it without ever choosing to. That is what makes it different from other substances. When you know what to watch for in yourself or your loved one, you can act before a dose turns fatal. The signs below are worth knowing now, not later.