I am not sure how accurate those tests are. I am highly allergic to hydrocodone (Vicodin or Norco). So when the test came back positive for hydrocodone, I told them no way... someone screwed up.
A 2nd PA came into my room, and tried really hard to push me into admitting I took it... these tests are never wrong. (Statistic, statistic, statistic, blah, blah, blah). I just sat there until he shut up, and didn't say a word. For like 45 secs. Then very quietly, very slowly, said - "I HAVE NOT taken hydrocodone in 15 years. I am highly allergic."
After not saying another thing... he left my room. My regular PA was standing in the room, trying not to laugh. She & I had already talked, but she had to bring in a 2nd person. (Office policy)
In your case, forewarned is forearmed. Most pain management offices have a set timeframe for testing. Be prepared for a second test. Cut back on your fluids for the day before & of the next several appts. Just be ready to CALMLY state, I take my meds as prescribed. If the next several tests are fine, then cutting back the meds is your best option prior to testing.