As the death toll from the nation’s opioid crisis swells, California officials have launched an experiment: paying for people to test their drugs for fentanyl. Fentanyl, an opioid that is up to 50 ...

Illicit drug users who are certain that fentanyl is mixed into the heroin they consume are much more likely to take precautions that reduce their chances of overdosing, researchers reported Wednesday ...

In New York, fentanyl test strips are becoming more common as a way to fight an overdose crisis, and more states are pushing to legalize them. But not all users are trying to avoid the powerful drug.