Drugs may contain deadly levels of fentanyl, and you wouldn't be able to see it, taste it, or smell it. It is nearly impossible to tell if drugs have been laced with fentanyl unless you test your drugs with fentanyl testing strips. Testing strips are inexpensive, typically give results within 5 minutes, and can be the difference between life or death. Even if the test is negative, caution should be taken as test strips might not detect more potent fentanyl-like drugs, like carfentanil.3