How long does it take for fentanyl to come out of your system?

Short: Fentanyl is a synthetic opioid medicine with a short half-life on the order of 30 minutes. Extarpolating the math, one would expect 90%+ of a single administration to be cleared from a person within a couple of hours.L assuming normal metabolic parameters.

short acting drug: Fentanyl is a short acting narcotic with a half-life of 20min in serum. The effects are usually gone in about 60min. If your question relates to urine metabolites as in drug testing, it is not usually assayed as a drug of abuse. Fentanyl is essentially absent in urine approximately 72hr after administration.