I've only heard of dxm showing positive for pcp and opiates, pcp showing positive more rarley than opiates. I personally don't know how comapnies react, I assume it varies.
Also from the same link:
"11. IF YOU FAIL
If you fail the test, raise hell. Failing the drug test has been known to make a quiet person go ballistic. You will be interviewed by a medical review official (MRO), who would try to find out why you tested positive. MRO's are NOT impartial. An MRO is an employee of the lab, and is there for quality control. They are also there to protect the lab by coercing the court into thinking that the person who failed is a drug abuser. "Anything you say to an MRO can and will be used against you" (RDW). If you fight it, your lawyer "can subpoena the proficiency testing records of the laboratory for review" (anon1). These questions should be asked about the lab you are challenging:
How does the lab handle samples? Are they NIDA/CAP certified? Do they participate in appropriate proficiency testing? Whay is their track records in the proficiency testing program? Have they ever failed a proficiency test? What are the qualifications of the technical staff performing the test? What technologies do they use to screen and confirm?
"Conquering the Urine Tests" provides additional legal advice that will help you before taking a test, and if you fail a test.
Laura Gibson, a medical doctor on the internet, tested positive and was not hired. She had a poppy seed bagel that morning, not knowing it was a false positive. She fought it to the point where they just decided to throw out the results and hire her anyway. But don't go taking it to court; it's virtually impossible to win this case.
If you're an adult, contact ACLU. If you're a child, don't bother; ACLU won't do anything for children who fail the drug test. Then mail me at and tell me what you tried so I can use that to help others. Many people ask for advice before the test, then don't report back.
There is a way to fight drug testing. If you ever serve as a juror for a case where someone is being charged for a drug offense, and a drug test is used as evidence, be aware of jury nullification. If sufficient evidence is submitted supporting a law you consider unjust, you have a RIGHT to vote not-guilty, simply because you disagree with the law. You may agree with the law, yet disagree with the punishment for that particular crime. If you feel the punishment will be too harsh, you also have the right to vote not-guilty. Vote your conscience. The court never tells the jurors of this [hidden] right, but it's there. The Fully Informed Jury Association is a good source for this information.
Many employers no longer show lab results to employees. They just get rejected if seeking employment. Elderly employees are getting fired for failing the test; incidentally losing all of their pension benefits."
Of course this is if the lab shows a false positive, which is A LOT rarer than a panel having an error, but it can happen.