most helpful answer first of all stop taking your xanax other than as prescribed. if you're having anxiety problems (which is what xanax is prescribed for) and the evening dose is not controlling your anxiety you should talk to your provider about better therapies for your issue. that said you may be off the hook. urine drug tests are generally given as a pass/fail type of test. these tests generally don't measure the level of a given substance in your urine. you either have xanax in your urine or you don't. since you have a valid prescription for xanax it would be presumed the drug test would detect it in your system. but again you need to stop taking xanax during the day especially if you're in a job where you operate machinery or drive trucks. you potentially jeopardize yourself and others when you take prescription medications irresponsibly. take care of yourself!
can a lab tell the time of day you took prescription xanax. i have a prescription to take 2mg xanax only at bedtime. i took 2. 5 mg at 10am and. 5 mg at 2pm. i took a urine test at 4pm. this was a d. o. t urine test where they sent it to a lab and i will be screwed if they find out that i took it during the day. will they know? thx