DOT urine samples do not test for drugs. Well at least here in California, but DOT is federal guidelines. They just test for specific gravity, protein, blood and sugar.

Reason stated on medical form - "Protein, blood or sugar may be an indication for further testing to rule out any underlying medical problem."

This is from the DOT physical itself. If you're having a drug test administered by order of the DOT, then that is something different. I got paranoid for a while having to stop every 2 years to renew my medical, but I went in yesterday dirty as hell and walked right out, results in hand.