How long does Fentanyl stay in your system?

Fentanyl is a synthetic opioid analgesic, dispensed via prescription to treat moderate-to-severe pain. Fentanyl most commonly comes in pill form, as well as a patch. Fentanyl patches are changed out every 48 hours, as needed to manage pain. Fentanyl is a drug that is 50-100x more potent than morphine, and can be very dangerous. Due to its intensity, side effects include addiction and risk of overdose (more on Fentanyl withdrawal).

Fentanyl’s Half Life

How long a drug remains active in the system is its half-life, which is half the duration of time the drug is actively working. Fentanyl has a half-life of 3.5 (IV) hours or up to 3 to 12 hours (Patch). This is the amount of time it takes for half a dose of Fentanyl to leave one’s system. It may take an average of 22 hours to eliminate all of the Fentanyl from the system. However, this can take longer for those who are long term users of Fentanyl.

How long does Fentanyl stay in your system?

  • Blood: Up to 48 hours
  • Saliva: Unable to use for Fentanyl
  • Urine: Up to 3 days
  • Hair: Up to 90 days

Factors That Determine How Long Fentanyl Stays in the System

A handful of considerations calculate how much Fentanyl is in a person’s body, such age, height, weight, and body mass index (BMI). The amount of the drug taken, as well as the duration also play a significant role. Different biological factors also can affect the timeline in which Fentanyl stays in a patient’s system.


In conclusion, the period that Fentanyl remains in a patient’s body depends on many influences, such as the type of drug test administered and individual biological factors of the patient. Different drug tests will provide different time frames, so this must be considered. The dosage, as well as the length of time the patient has been on the Fentanyl also determines how long the drug remains in the body, among other factors.