I made a mistake with my calendar. I'm supposed to change patch every 3 days, but I forgot and didn't replace my patch until later on the 4th. I had my urine test sent in on that 4th day and I just realized what I did! It would be ok but I want to make sure the fentanyl test comes back positive from the lab. I've been a FAITHFUL pain management patient for almost two years and it would crush me if my doctor didn't trust me. I have never had this issue before so I don't know if it's possible to leave your system that fast! I hope not. If you have any experience to share I would be grateful. Thanks so much.