This is only my experience, but here goes...I was given a random at work a few months ago. My employer knew that I had severe back problems, and had just come back from medical leave (anybody else smell a setup?)and I had had radio frequency nerve ablasion done 10 days before. I told them I had a script for Klonopin and Hydro, but the test came back showing both Klonopin AND Valium! Initially, I simply had no explanation for it...but then I remembered that when I had the nerve ablasion procedure I received IV sedation. I am SURE that that is where the Valium came from, since I hadn't taken any, and the stuff can stay in your system for up to 6 weeks! I tried explaining this to them, but to no avail. I was referred to a drug treatment center (while I was still under the care of a pain management specialist mind you)and told that I had to go off all of my meds in order to keep my job! Ua tests are SUCH BS if they are trying to hang somebody, because it doesn't prove that I was under the influence on the job,(i MOST DEFINITELY WASN'T) just that it was detected in my urine...which with hydro can be up to 36 hours, and benzos much longer. Needless to say, I told them to take their job, and their 'treatment plan' and shove it!