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How Long Does Fentanyl Stay in Your System?

It’s difficult to truly know how long fentanyl stays in your system. We know that laboratory-made fentanyl patches have a half-life of three to 12 hours, and we know most drugs are rendered inactive after four to five half-lives. Based on that data, we can estimate that fentanyl patches last for 12 to 60 hours.

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However, oral forms of laboratory-made fentanyl have different half-lives. Troublingly, we also know that illegal fentanyl can be stronger than lab versions or contaminated with other substances that change half-life estimates.

Keep reading to learn best estimates of  how long fentanyl stays in your system, how long it shows up on a drug test, and why this information is so important.  

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.

Fentanyl is extremely dangerous. Synthetic opioids like fentanyl were responsible for nearly 71,000 overdose deaths in 2021. The rate of overdoses involving these drugs in 2021 was 22 times the rate seen in 2013.

 Two main types of fentanyl exist.

Legal (Prescription) Fentanyl

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.

Prescription-grade fentanyl is powerful, and patients are given detailed instructions about how to use it and what drugs to avoid while on fentanyl. For example, people using fentanyl patches are reminded that their drug shouldn’t be used with benzodiazepines or other central nervous system depressants, as these combinations can cause life-threatening overdoses.

Illegal (Illicit) Fentanyl

Fentanyl is a controlled substance, but the ingredients (precursors) dealers need to make it are not always banned or regulated. As a result, dealers can buy what they need from companies in Mexico or China and produce illegal drugs they can sell to unsuspecting people anywhere in the world.

Illicit fentanyl comes in several formats, including liquids and powders. Dealers may sell their substances as fentanyl, or they may tell their customers they’re buying something else (like Vicodin) when the products contain nothing but fentanyl.

Illicit laboratories may not have strict quality-control measures, so it’s difficult to know how strong each product is and how long it might last. Experts say most cases of fentanyl-related overdose are linked to illicit fentanyl made in labs like this.

People who buy fentanyl from dealers rarely (if ever) get documents about what’s inside their drugs or how to use them. They may not realize that combining their drugs with other substances could cause death. They may not even realize that the drug they’re about to take has fentanyl inside it.

Fentanyl Half-Life Details

A drug’s half-life is a measurement of how long the body needs to process about half of the dose. When four to five half-lives have passed, the drug is rendered inactive within the body.

Laboratory fentanyl half-lives can vary by the method in which it’s administered. This table can help you understand those differences:

Method of AdministrationHalf-Life
Injection3.65 hours
Patch3-12 hours
Lozenge7 hours

No firm estimates on the half-life of snorted fentanyl or fentanyl powders exists, as these products are made in illegal laboratories and aren’t tested by the U.S. Food and Drug Administration. They could last for shorter or longer periods, but no one is quite sure.

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 fentanyl 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 February 13, 2024
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