what can you do if you take a drug test and it come back with a false postive

i took a drug test and it came back false positive for meth. i was not asked if i was taking any kind of medication and i forgot to mention i had taken some and i even showed the doctor what i had take and was told it didn't make a difference.

i've looked it up on the internet and the OTC meds i took will come up positive but they said that its not possible. is there anything i can do to get this cleared up.