How long does fentanyl stay in your system?

I don’t know the scientific answer, only the personal experience answer. I was on a fentanyl patch for 5 years and had my Dr lower my dosage until I was at the lowest mcg. I kept the patch on until it fell off and never applied another one. My withdrawals were terrible for a week straight, but I had withdrawal like side effects for over a month. Fentanyl is a nightmare & really shouldn’t be given to people with chronic pain. It was created for people dying, not the living. Good luck!