How Long Does Fentanyl Stay in Your System?

Last Updated: February 16, 2024

Editorial Policy | Research Policy

Fentanyl can stay in your system anywhere from hours to months, depending on the fentanyl dosage form and what is being tested.

Drugs can stay in your system for different lengths of time. Medications are also often formulated differently, with some dosage forms lasting longer than others and some drug tests picking up drug traces for longer. Because fentanyl is a medication with several different dosage forms, it is important to consider the dosage form you are using if you take fentanyl and are wondering how long it lasts in your body.

What Is Fentanyl? 

Fentanyl is a Schedule II opioid narcotic. It is one of the most potent opioids and is 100 times stronger than morphine and 50 times stronger than heroin. When prescribed by a doctor, it is used to treat acute and chronic pain, including pain from cancer. 

Fentanyl is also available illicitly and is sometimes mixed with other street drugs, significantly increasing the risk of overdose on those substances.

How Does Fentanyl Work? 

Fentanyl works by binding to the mu opioid receptors in the central nervous system, although experts are not sure specifically how it achieves its effects. As a central nervous system depressant, fentanyl has several different side effects alongside its analgesic effects. These include:

  • Headache
  • Nausea and vomiting
  • Constipation 
  • Sleepiness or fatigue
  • Confusion
  • Weakness
  • Dizziness
  • Trouble breathing 
  • Swelling
  • Redness and skin rash (skin patch dosage form only)
  • Pain or irritation in the mouth (buccal tablets dosage form only)

How Long Does Fentanyl Last? 

Fentanyl is available in different dosage forms and starts working quickly. The drug can last different periods depending on the dosage form used. Your age, overall health, weight, body chemistry and opioid tolerance will also play a role in determining how long fentanyl lasts. In general, fentanyl’s duration is as follows:

Fentanyl dosage formHow long it lasts
Injectable (given in hospitals only)30–60 minutes
Lozenge4 hours
Intrabuccal tablet4 hours
Sublingual tablet2 hours
Sublingual spray4 hours
Nasal spray2 hours
Skin (transdermal) patch72–96 hours

Fentanyl Half-life

A drug’s half-life refers to how long your body takes to clear half of a single dose from your system. However, half-lives differ depending on the dosage form, and because fentanyl has different dosage forms, it has different half-lives. It typically takes five half-lives for a drug to leave your system completely. Therefore, half-lives can help you predict how long fentanyl may stay in your body.

Fentanyl dosage formHalf-life
Lozenge3.2–6.4 hours
Intrabuccal tablet2.6–11.7 hours
Sublingual tablet5–13.5 hours
Sublingual spray5.3–12 hours
Nasal spray15–25 hours
Transdermal patch20–27 hours

Fentanyl Drug Testing

Sometimes, a fentanyl drug test may be required under one of several different conditions:

  • Employment drug screening by your employer
  • Medical drug screening by your doctor
  • Criminal justice drug screening by the legal system

Fentanyl does not typically show up on many standard drug tests, even when they test for opioids, so fentanyl-specific drug tests need to be ordered to find the drug in your system. This is because fentanyl is a synthetic, or manmade, opioid with different chemistry than natural and semi-synthetic opioids that are more likely to appear on drug tests. 

Several different factors can impact how long fentanyl shows up in your system, including:

  • Fentanyl dose
  • How often you take fentanyl
  • Route of administration
  • Fentanyl dosage form
  • Your age
  • Your body composition 
  • Your sex
  • Your medical history
  • Other medications you take
  • Your hydration and nutritional status

How Long Does Fentanyl Stay In Your Urine? 

Fentanyl stays in your urine for one to three days. Its breakdown product, norfentanyl, can also be found in urine for the same time.

How Long Does Fentanyl Stay In Your Saliva?

Experts aren’t sure how long fentanyl can be detected in your saliva, although they agree it stays in your saliva for a shorter time than in your urine. However, most drugs that appear in saliva can be found as long as 24–36 hours after use.

How Long Does Fentanyl Stay In Your Blood?

Traces of fentanyl can be found in your blood from 3–12 hours after the last dose of the drug. Fentanyl’s breakdown product, norfentanyl, can be found in the blood for a narrower timeframe, between nine and 10 hours.

How Long Does Fentanyl Stay In Your Hair?

Fentanyl can stay in your hair for a long time. A one-and-a-half-inch hair sample can show if fentanyl was used in the past 90 days.

Find Help for Fentanyl Addiction

If you have an upcoming drug test and are worried about fentanyl showing up on it, this could be a sign of fentanyl addiction. Fortunately, help is available at The Recovery Village Cherry Hill at Cooper. From our medical detox program to cleanse your system of fentanyl to our rehab program to teach you how to live a fentanyl-free life, we are with you every step of the way. Contact a Recovery Advocate today to learn more.

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Hallare, Jericho; Gerriets, Valerie. “Half-Life.” StatPearls, June 23, 2022. Accessed April 14, 2023.

Gryczynski, Jan; Schwartz, Robert P; Mitchell, Shannon D; et al. “Hair Drug Testing Results and Self-reported Drug Use among Primary Care Patients with Moderate-risk Illicit Drug Use.” Drug and Alcohol Dependence, May 17, 2014. Accessed April 14, 2023.

ARUP Laboratories. “Drug Plasma Half-Life and Urine Detection Window.” September 2022. Accessed April 14, 2023.

LabCorp. “Drug Test Summary for Urine Oral Fluid and Hair.” Accessed April 14, 2023.

ARUP Laboratories. “Therapeutic Drug Monitoring.” February 2023. Accessed April 14, 2023.

ARUP Laboratories. “Drug Testing.” August 2022. Accessed April 14, 2023.

Griswold, Matthew K.; Chai, Peter R.; Krotulski, Alex J.; et al. “A Novel Oral Fluid Assay (LC-QTOF-MS) for the Detection of Fentanyl and Clandestine Opioids in Oral Fluid After Reported Heroin Overdose.” Journal of Medical Toxicology, October 2, 2017. Accessed April 14, 2023.

Department of Justice, Drug Enforcement Administration. “Drug Fact Sheet: Fentanyl.” March 2023. Accessed April 14, “FentaNYL Monograph for Professionals.” March 3, 2022. Accessed April 14, 2023.

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