Got a drug test today to see if i was taking my narcotics or selling them will weed show up?

I smoked 3 days ago... and the doctor drug test me to test and see if i was taking my xanax. or selling them i guess... but anyways... will weed show up in the test... if they are testing for narcotics... or will it show up... they sent it to a lab... they didnt do test there... and if it shows up what can the doctor do?