You want to avoid saying you do not have an issue with random drug tests if you use drugs, and the tests will come back positive. If you use drugs, you will be wasting the company's time and resources to hire and train you to turn around and let you go when a test comes back positive. If you use drugs, you might want to reconsider applying to jobs that require drug testing until you can become clean. If you use medicinal marijuana and have a doctor's prescription, describe your situation and let the interviewer know the tests might return positive for marijuana. The interviewer can then decide if that will be an issue with the company's policy.

"No, I do not have an issue with random drug testing. However, I want to be honest and let you know I have a doctor's prescription for medicinal marijuana. I use three drops of a tincture every night to help me sleep, but it does not interfere with my work, and I never use marijuana while on the clock. My last employer was aware of my prescription, and they can attest that using the tincture never interfered with my job."