Can taking percocet for back pain cause liver and kidney damage? been taking for almost a year. less than prescribed but at least one a day.

Highly unlikely: The oxycodone is Percocet is not the cause of the problem - it is the tylenol (acetaminophen). One tablet contains 325 mg of tylenol, and that is not enough, even daily, to cause harm in someone who is otherwise healthy and not on other medications or substances (like alcohol in excess) that can damage liver or kidney. Look into non-opiate ways to treat pain:physical therapy, weight loss,exercise.