What can cause a positive result for meth on a drug test? I have NEVER done drugs! I took Fioricet with Codeine for a headache less than a week ago and wonder if this could have caused it.

Did you show the office the prescription for the medication you took... BEFORE the test?

All you have to do, so provide them the prescription in your name. If this was not yours, but you got it from someone else, it is also considered illegal drug, since it was not yours.

It is possible that Fioricet with codeine could cause a false positive on an EMIT immunoassay (IA). But not likely and never on confirmation testing. So the Fioricet wouldn't be my first guess.

Where did you get the idea that the test was positive for meth? An initial IA only reports on categories, therefore a "presumed positive" would be for amphetamine, not methamphetamine. A "presumed positive" requires a confirmation test where there are no false positives.

The most common false positives occur in the amphetamine category(1) and only at the IA level. These are easily cleared up by confirmation testing. That is what you should immediately request.

1) Brahm, 2010 Commonly Prescribed Medications and Potential False-positive Urine Drug Screens, American Journal of Health-System Pharmacy. 2010;67(16):1344-1350