I'm on oxycodone. my urine test came out negative though i'm taking it regularly. can it be because the had the test 5 days after collecting my urine?

Possibly.: There are three potential explanations. 1.Oxycodone metabolites are usually undetectably after 72 hours especially if the urine is dilute. 2. The test did not include synthetic codeines like oxycodone. 3. If this was a mandated drug screen that required chain of custody (like for the DOT ) it would be reviewed as negative (even though detectable) if you have a legitimate Rx.