How Long Does Fentanyl Stay in Your System?

3 min read · 7 sections

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Fentanyl is a powerful prescription opioid used to treat severe pain. Rates of fentanyl abuse have escalated in recent years, leading to an increase in overdoses and deaths. Some fentanyl is diverted from medical purposes for illicit use; however, much of the street supply of fentanyl is manufactured illegally.


Fentanyl will usually show up on a urine test between 24-72 hours after last use. Hair tests can detect the drug for up to 3 months, and blood tests can detect it between 5 and 48 hours after use depending on the dose.

Overdose is a serious concern with fentanyl, particularly since it is often combined with other substances. People who become addicted often require treatment with medications and/or therapy to help them quit using.

What Is Fentanyl?

Fentanyl is a synthetic opioid drug that is prescribed to treat severe pain, such as advanced cancer pain or chronic pain in patients who are tolerant to other, less potent opioids. 2 It is approximately 50 to 100 times stronger than morphine.1

Pharmaceutical fentanyl is available in several forms, including transdermal patch, lozenge, nasal spray, tablet, and injectable solution.3 Illicit fentanyl is usually found in powder form, as a tablet, spiked on blotter paper, or mixed with other drugs.2

People may swallow, snort, or inject illicit fentanyl. Some place the blotter paper in their mouth, where it is absorbed through the mucous membranes.2

Fentanyl overdoses are on the rise. In 2017, more than 28,000 deaths in the United States involved synthetic opioids.1 From 2016 to 2017, deaths from synthetic opioids significantly increased in 23 states and the District of Columbia. Reports indicate that these increases are largely driven by fentanyl overdoses—specifically, illicitly made fentanyl.1

The difference between a safe dose of the drug and one that can cause an overdose is quite small. Additionally, fentanyl is often mixed with cocaine or heroin without the user’s knowledge, making it even more dangerous.2

How Does Fentanyl Work?

Fentanyl attaches to and activates certain opioid receptors, which are located in areas of the brain that affect pain and emotion. Through its interaction with these receptors, fentanyl also increases the release of dopamine from certain nerve cells in our brain’s reward center.2 This resulting increase in dopamine activity is associated with a reinforcing sense of euphoria. However, the drug can also slow breathing, which, given fentanyl’s potency, greatly increases the risk of overdose.2

Is Fentanyl Drug Tested For?

Drug testing is conducted for many different reasons.

  • Some employers require drug testing before hiring or periodically throughout employment to monitor drug use.
  • Drug testing may also be ordered in the case of legal situations that need to be investigated like a crime or car accident.
  • Healthcare professionals may drug test to make sure a patient is taking the right dose of their medication.4

How Long is Fentanyl in Your System?

While the effects of fentanyl may only be felt for a few hours, traces of the drug remain in the system for much longer and can show up on a drug test. Additionally, dose, duration of use, frequency of use, weight, urine concentration, and impaired kidney or liver functioning can all affect detection time.5

There are a number of drug tests that are used to detect fentanyl, including urine, hair, and blood tests. A person can test positive for fentanyl on a urine test for 24­–72 hours after last use.6 However, norfentanyl, a metabolite created in the process of breaking down the drug in the body, can be detected for up to 96 hours.6 Hair tests can detect for fentanyl for up to 3 months after last use.7 Blood tests are able to detect fentanyl use from 5 hours to 48 hours after last use.8

Saliva tests are used to test for many drugs. In the case of fentanyl, however, saliva tests cannot consistently detect it or its metabolites.6

Body System Time in System
Blood 5-48 hours
Hair Up to 3 months
Saliva Not consistently detected
Urine 24-72 hours

What Happens if You Take Too Much?

Fentanyl’s potency makes overdose a real possibility, especially if the person uses it thinking it is another drug.2 Combining substances such as alcohol and benzodiazepines (Xanax, Klonopin, Valium) with fentanyl also increases the risk of overdose and death by respiratory arrest.9

An overdose can be fatal. Call for medical help immediately if you suspect one. Medical professionals can administer naloxone, an opioid receptor blocker that acts as an “antidote” to reverse the effects of opioids. Naloxone is available in several formulations—depending on the setting, it may be administered via an intravenous or intramuscular injection or as a nasal spray.

For some regular opioid users, it may possible to keep naloxone at home in case of an overdose. It is unlikely that a person would be able to administer naloxone themselves during an overdose, so it is important that family members and loved ones are familiar with how to use the medication in whatever formulation is on hand.10

How Can You Safely Stop Taking Fentanyl?

Individuals who have developed significant physical dependence on fentanyl are likely to experience withdrawal symptoms when they try to go off the drug. The severity of withdrawal symptoms will vary depending on the length and intensity of use.

Fentanyl withdrawal symptoms may first begin within 12 hours after their last use. Withdrawal symptoms can last for up to a week, with the first 3 days usually the most difficult.10

Dealing with withdrawal symptoms for Fentanyl on your own can be extremely difficult and dangerous. Asking for help is an important step towards a healthier lifestyle, and American Addiction Centers is here to guide you through this journey. Call us at

Typical fentanyl withdrawal symptoms include:10

  • Irritability.
  • Feelings of depression.
  • Loss of appetite.
  • Trouble sleeping.
  • Increased blood pressure.
  • Increased heart rate.
  • Nausea.
  • Vomiting.
  • Diarrhea.
  • Runny nose.
  • Watery eyes.
  • Weakness.
  • Chills.
  • Muscle pain.

Fentanyl Addiction Treatment & Medications

mental health assessmentSubstance abuse treatment approaches have evolved to better help those impacted by the increasingly widespread opioid epidemic, which includes the misuse and abuse of prescription painkillers as well as drugs like heroin and illicit fentanyl and its analogs. Common treatment methods used to help people recover from opioid addiction include several medications approved for opioid dependence and various behavioral therapies. Therapy and counseling combined with medication may increase the effectiveness of treatment.11

  • Buprenorphine (which can be administered alone or in combination with naloxone, as Suboxone) and methadone are also opioid receptor agonist drugs, meaning that, to differing extents, they activate the same receptor system that fentanyl acts on to reduce the intensity of cravings and withdrawal symptoms. Naltrexone, which is sometimes used post-detox, is what’s known as an opioid antagonist—it also binds to opioid receptors but, in doing so, prevents fentanyl from producing effects.11
  • Behavioral therapies help people adjust thinking patterns and behaviors around fentanyl use, develop better coping skills, and more adaptively react to any triggers that are encountered. Cognitive behavioral therapy is perhaps the most well-known of these therapies.11

If you’re concerned about the dangers of fentanyl or struggling with any type of opioid abuse, get help today. A variety of programs are available across the country that offer flexible schedules, levels of intensity, and different payment options. Users who experience symptoms of withdrawal can undergo a medically supervised detox program and then after stability is achieved, move into an inpatient or residential program where therapy and long-term treatment can start.


  1. Centers for Disease Control and Prevention. (2018). Fentanyl.
  2. National Institute on Drug Abuse. (2016). Fentanyl.
  3. Drug Enforcement Administration. (2017). Drugs of Abuse.
  4. U.S. National Library of Medicine, Medline. (2017). Drug Testing.
  5. Moeller, K., Kissack, J., Atayee, R., and Lee, K. (2017). Clinical Interpretation of Urine Drug Tests: What Clinicians Need to Know About Urine Drug Screens. Mayo Clinic Proceedings.
  6. Silverstein J.H., Rieders, M.F., McMullin, M., Schulman, S., Zahl, K. (1993). An analysis of the duration of fentanyl and its metabolites in urine and salivaAnesthesia & Analgesia, 76(3), 618-21.
  7. MedlinePlus. Toxicology Screen.
  8. Schwartz J.G., Garriott J.C., Somerset J.S., Igler E.J., Rodriguez R., Orr M.D. (1994). Measurements of fentanyl and sufentanil in blood and urine after surgical application. Implication in detection of abuseAmerican Journal of Forensic Medicine and Pathology, 15(3), 236-41.
  9. Harm Reduction Coalition. Mixing Drugs.
  10. Alcohol and Drug Foundation. Fentanyl.
  11. National Institute on Drug Abuse. (2018). Prescription Opioids.
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