I am taking Adderall rx for ADHD. I may have to take a drug test for a job. Will this cause a false positive? For what? Should I just bring my prescription with me?

The recommendation is to tell your employer about any prescription drug you are taking that may show up on a drug test. Adderall is a stimulant and is likely to show up as a stimulant on drug testing, so your employer needs to know you are taking a legitimate prescription.