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How Long Does Fentanyl Stay in Your System?

Fentanyl can stay in your system for between 11 and 36 hours, but it is typically only active for between 30 and 60 minutes.

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How you take fentanyl influences how long it remains active or stays in your system. For example, injecting fentanyl is the quickest route of administration, and it will also clear your system faster. Other methods of fentanyl administration include transmucosal (through a sublingual or buccal tablet or lozenge) or a controlled-release transdermal patch that releases fentanyl slowly over a period of 72 hours to keep the drug active for longer. 

In general, fentanyl will only stay in your system for a matter of hours, up to 36 hours in total.

What Is Fentanyl?

Fentanyl is a powerful and potent synthetic drug with a fast onset of action. It can start working within a minute of taking it. Depending on how it is administered, it can also clear out of your system fast — within a few hours. 

As a synthetic opioid drug that is up to 100 times stronger than morphine, fentanyl is most commonly clinically used to treat breakthrough cancer pain in patients who are already taking a narcotic for pain relief and are opioid tolerant. 

Opioid tolerance occurs when taking opioid drugs regularly. The brain becomes accustomed to the drugs, meaning that doses that were effective before no longer will be. Fentanyl is an option to treat this kind of significant pain that can no longer be controlled by other methods or medications. 

Fentanyl is a prescription opioid medication. It is a Schedule II controlled substance by the Drug Enforcement Administration (DEA) due to its high potential for diversion, abuse, dependence, and addiction. 

It is prescribed carefully and closely monitored by a medical professional in patch, lozenge, buccal tablet, sublingual tablet, and injectable forms. The drug is also commonly made illicitly in clandestine laboratories for recreational use. 

Fentanyl is extremely dangerous. Synthetic opioids like fentanyl were involved in nearly 60,000 opioid overdose deaths in 2020.

Fentanyl Half-Life Details

Fentanyl has a general half-life of between 8 and 10 hours. Half-life is the amount of time it takes for your body to break down and eliminate half of the drug from your system. The drug will commonly remain in your body for double the half-life, so in this case, fentanyl often remains in your system for between 16 and 20 hours. 

The half-life of fentanyl, and how long it remains in your system, can be influenced by how you take it. Differences in half-life based on route of fentanyl administration are as follows:

  • Intravenous (IV) fentanyl: 2–4 hour half-life
  • Transmucosal fentanyl (buccal and sublingual tablets and lozenge): 5–14 hours
  • Transdermal patch: approximately 13–22 hours

What Are the Different Drug Tests Used to Detect Fentanyl?

Fentanyl can be detected on four different types of blood tests.

  • Blood: For this test, a small amount of blood is drawn to test for the presence of fentanyl. Blood testing is a more invasive form of drug testing.
  • Hair: This is one of the least invasive types of drug testing that involves testing a strand of hair. It offers the longest detection window.
  • Saliva: With a very short window of action, this test takes a sample from inside your mouth and can potentially detect same-day drug use.
  • Urine: This is one of the most common methods of drug testing. With a urine test, your urine will be tested for drug metabolites. The drawbacks of this test are concerns with tampering.

How Long Does Fentanyl Last in Your System?

Type of Test Length of Time Detected
Blood5–48 hours
HairUp to 3 months
SalivaNot generally detectable
Urine24–72 hours

Factors That Determine How Long Fentanyl Stays in Your System

How long fentanyl remains in your system can be influenced by a variety of factors, which can include the following:

  • Route of administration: patch, lozenge, tablet, or recreational use
  • How it was taken: swallowed, snorted, smoked, or injected
  • Genetic and biological factors: personal metabolism, any underlying medical or mental health conditions, or additional contributors, such as age, body fat, weight, and race
  • Opioid tolerance or dependence: This can influence how fentanyl interacts in your body. The longer you have been taking fentanyl, the longer it will stay in your body. 

How Do You Safely Detox From Fentanyl?

Fentanyl is an extremely powerful opioid drug that should not be stopped suddenly due to the potentially life-threatening withdrawal symptoms that can occur. To safely detox from fentanyl, the drug is often replaced with a different opioid drug. 

Often, this is one of the medications used in medication-assisted treatment (MAT), such as buprenorphine or methadone. These medications can help to keep opioid receptors in the brain activated to control cravings and withdrawal symptoms. 

Detox is optimally performed in a specialized detox center or addiction treatment facility that can provide medical and medication management as well as mental health support and around-the-clock supervision. The goal of detox is physical stabilization before entering into a complete addiction treatment program. 

How to Get Help for Fentanyl Addiction

Fentanyl is a highly addictive drug that can be habit-forming even when taken as directed through a legitimate and necessary prescription. Fentanyl addiction is best managed through a comprehensive addiction treatment program that can offer the following:

  • Medical detox
  • Medication management
  • Support for any co-occurring disorders
  • Group and individual therapy and counseling 
  • Educational programs
  • Life skills training
  • Relapse prevention tools
  • Support groups

To find a treatment program or provider near you, try the Substance Abuse and Mental Health Services Administration (SAMHSA) treatment locator. This resource can help you locate local options for opioid addiction treatment and support. Opioid addiction is highly treatable.

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Medically Reviewed By Dr. Alison Tarlow

Dr. Alison Tarlow is a Licensed Clinical Psychologist in the States of Florida and Pennsylvania, and a Certified Addictions Professional (CAP). She has been a practicing psychologist for over 15 years. Sh... Read More

Updated June 8, 2023
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  2. Drug Scheduling. Drug Enforcement Administration.
  3. Synthetic Opioid Overdose Data. (June 2022). Centers for Disease Control and Prevention.
  4. Opioid Half-Lives and Hemlines: The Long and Short of Fashion. (May 2016). Anesthesiology.
  5. Fentanyl, Fentanyl Analogs and Novel Synthetic Opioids: A Comprehensive Review. (October 2017). Neuropharmacology.
  6. Behavioral Health Treatment Services Locator. Substance Abuse and Mental Health Service Administration.
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