How long does fentanyl stay in your system
How long does it stay in your urine.
Fentanyl has a sort half life, partially depending on the way it is given. Injectable Fentanyl's half life is about 4 hours, so a single 50mcg dose is probably undetectale in urine within 2 days. Longer dosing periods could run this up to 34 days, and multiple day
administration of Fentanyl by a topical patch could extend this to 5 days.
There are a lot of variables, so it is difficult to predict without knowing your own personal physiological parameters, total dose received, and by which route, etc.
Certain disease conditions, impaired renal function, impaired liver function, could extend these times longer.