How Long Does Fentanyl Stay in Your System?

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Fentanyl is a synthetic opioid that is commonly prescribed for the management of severe pain. Although fentanyl is similar to other opioids like morphine, heroin, and oxycodone, it can be from 50 to 100 times more potent than morphine.

The potency of fentanyl means that the synthetic opioid is frequently indicated in clinical settings, especially for treating severe pain in cancer patients or following surgery. In the past decade, fentanyl has also become a drug of abuse. Data from CDC (Centers for Disease Control and Prevention) indicate that fentanyl was implicated in 71,000 of the 107,000 fatal drug overdoses in the United States in 2021.

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How long does fentanyl stay in your system, though?

Fentanyl Half-Life

One of the main factors that influence how long fentanyl stays in your system is its elimination half-life. The half-life of a drug is the length of time it takes for blood concentration levels of the drug to be reduced by 50%. It takes from four to five half-lives for all of a substance to be purged from the system.

What is the Half-Life of Fentanyl?

Fentanyl has a half-life of three to seven hours. The half-life of Fentanyl will vary depending on how your body processes and eliminates drugs.

The sustained use of fentanyl causes the drug to accumulate in fatty tissues throughout the body. This can prolong the rate of elimination of fentanyl from the body.

Opioids like fentanyl with short half-lives are associated with more severe withdrawal when use is discontinued.

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How Long Does Fentanyl Stay in Your System For?

The effects of fentanyl subside after a few hours, but traces of the synthetic opioid will linger in the system for longer.

Detection time will depend on the type of drug test used and factors such as:

  • Dose
  • Duration of fentanyl use
  • Frequency of fentanyl use
  • Urine concentration
  • Impaired liver or kidney functioning

How long does fentanyl stay in your system, then?


Fentanyl and fentanyl metabolites may be detectable in urine within two or three hours of using the synthetic opioid. Fentanyl will remain detectable in a urine screen for one to three days after use.


Hair testing can detect traces of fentanyl for up to 90 days, although it may take a few days to detect initial use.


Blood testing can detect oral fentanyl for three days, IV fentanyl for 20 hours, and transdermal fentanyl patches for up to three days.


It is challenging to detect fentanyl by using saliva samples, meaning that this test is not typically used to detect fentanyl.

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Opioid Rehab at California Detox

If you have developed opioid use disorder, we offer treatment programs at all levels of intensity at California Detox in Laguna Beach.

Take advantage of our supervised medical detox program and access medications to mitigate cravings and streamline the withdrawal process. Detox helps you conquer physical dependence on opioids and acts as a bridge to ongoing treatment. Choose from the following California Detox treatment programs for opioid addiction:

  • Inpatient programs (residential rehab)
  • PHPs (partial hospitalization programs)
  • IOPs (intensive outpatient programs)
  • Dual diagnosis treatment programs (for co-occurring disorders)

All treatment programs at our luxury beachside facility in Laguna Beach provide personalized opioid addiction treatment that combines evidence-based interventions and holistic treatments that include:

  • Psychotherapy
  • MAT (medication-assisted treatment)
  • Group therapy
  • Family therapy
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  • Aftercare

Call admissions today at 949.694.8305 for immediate help beating addiction to fentanyl or any other opioid.


The half-life of street fentanyl can vary depending on factors that include the method of administration, individual metabolism, and the presence of other drugs in the system. In general, the half-life of fentanyl is around 3 to 4 hours when injected, and 7 to 10 hours when taken via transdermal patches. That said, street fentanyl is often mixed with other substances like heroin, cocaine, or benzodiazepines, all of which can affect its half-life and increase the risk of overdose.
Fentanyl has been approved for medical use in the U.S. since the 1960s. Since then, the synthetic opioid has been used for surgical anesthesia and the treatment of severe pain. Janssen Pharmaceuticals, Mylan, Par Pharmaceutical, and Apotex Corp all manufacture fentanyl legally in the United States. Illicitly manufactured fentanyl is produced in clandestine labs in Mexico and China and then trafficked to the U.S.


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