Question: I've been unemployed and job searching the past few weeks. I have a medical marijuana card which I stupidly utilized during this break. Now that I have hit my final interview, I'm a little concerned. I've quit for a while but know it's still in my system.

I know excuses don't matter in the workplace, and a failed UA means you're not getting hired. My question: So I'm flying out of state for this last interview and they mentioned they'll take care of the hr stuff there. Is it possible to have an onsite drug test or will they most likely order one for me in my home state when I return?

Answer: 
In contrast to another answer, I wouldn't count on it, at least not while you're there. They're going to fly you out to an interview and then say "oh hey go over here for this drug test before your flight back"? 

I've actually had this exact situation come up... 3 out of the 4 jobs I took were in a different area than I was living at the time (2 out of state, 1 in a city 2 hours away). The drug test will probably come after you get an offer, and you can take it in your city. In my most recent case, the company they contracted with didn't have an office in my city, so they had me go to another company that they picked. This company sent the samples to their original company for the actual work.
I'm going to take the opposite opinion of some others and tell you not to worry about it until it comes up. Go to the interview as planned, and don't bring it up at all. I would not expect them to surprise you with a urine test at the interview, but I wouldn't entirely rule it out either. I would more likely expect that they require it within the first week of work, or that you schedule one with a testing facility.

If at some point they tell you that they will be giving you a drug test, then be honest about it. Try something like this:

> 
> Actually, since medicinal marijuana is legal in my state, I have a medical marijuana card to help me treat some personal health issues. I know that it can be detectable up to XX days after consumption, so there is a slight chance that I would fail that portion of the test. I understand that marijuana is not legal in this state though, and I most certainly would commit to not using in the future. If there would be problems with my test coming back positive for marijuana right now, could we delay the test until a later date?
> 
> 
> 

You want to be as factual and informed as possible. Know how may days it is possible to be detected. Know the laws in both states. Explain your illness if you feel comfortable. Show that you are a responsible legal user, not just some "pothead".