How Long Does Fentanyl Stay In Your System?

In recent years, the opioid crisis has brought attention to powerful substances like fentanyl. This synthetic opioid, originally developed for pain management, has gained notoriety for its potency and associated risks. Opioid use disorder affects more than 16 million individuals all over the world. The prevalence of this crisis emphasizes the importance of knowledge and understanding to prevent people from falling into opioid addiction.

One of the commonly asked questions is, “How long does fentanyl stay in your system?” To answer this, let’s delve into the intricacies of fentanyl and its presence in the human body.

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Fentanyl, particularly illegally-made ones, is also named as a major contributor to overdose cases in the United States. Despite this, fentanyl abuse continues to rise. According to the Centers for Disease Control and Prevention, fentanyl-related overdose deaths increased by over 22% from 2020 to 2021.

What is Fentanyl Used For?

Fentanyl, a synthetic opioid, has gained notoriety for being 50 times stronger than heroin and 100 times more potent than morphine. Its medical use primarily focuses on severe pain management in cancer patients and post-surgical settings. It binds to the body’s opioid receptors, primarily in the brain, which alters a person’s perception of pain. As a respiratory depressant, the drug induces a sense of euphoria and relaxation.

Pharmaceutical fentanyl is available in patches, lozenges, injections, and sprays. Meanwhile illegally made fentanyl (IMF) is available in different forms:

  • Powdered Form
  • Liquid Form (nasal sprays, eye drops)

In its powdered form, fentanyl is also often mixed with other drugs like heroin, cocaine, and methamphetamine, increasing their potency and danger. This also contributes to high overdose rates and drug fatalities. Due to its potency, even tiny amounts can be fatal, especially if unknowingly consumed.

Side Effects of Fentanyl Use

Fentanyl’s short-term effects include pain relief, euphoria, and sedation. However, misuse can lead to respiratory depression, confusion, and even overdose. On the other hand, extended use of the drug may result in tolerance, dependence, and addiction. Long-term effects can also include respiratory issues, cardiovascular problems, and mental health issues.

Question Box: What is the lethal dose of fentanyl?

The lethal dose of fentanyl can vary significantly depending on several factors including individual characteristics, route of administration, purity, and concentration. According to the Drug Enforcement Agency, 2 milligrams of fentanyl can be lethal. However, it is important to understand that even smaller amounts can be fatal for others. Any amount of fentanyl, especially when used outside a controlled medical setting, carries a significant risk of overdose and death.

Understanding Fentanyl Half-Life

A drug’s half-life indicates the duration of the drug to be reduced by half in the body. The half-life of fentanyl is relatively short, typically depending on the route of administration.

iv bag

Intravenous (IV)

2 to 4 hours

icon for capsules or medicine


3 to 12 hours

transdermal patch

Transdermal Patch

18 to 27 hours

sublingual spray

Sublingual Spray

5 to 12 hours

Factors Influencing Half-Life and Elimination

Dosage and Frequency of Use

The amount and frequency of fentanyl use directly impact its presence in the system. Higher doses and frequent use may lead to a more extended detection window.


Those with faster metabolism often eliminate substances more quickly. Fentanyl metabolism can vary, affecting the time it takes for the body to clear the drug.


Being well-hydrated can help flush fentanyl out of your system faster.

Other Health Conditions

Certain medical conditions can affect how your body processes fentanyl.

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While half-life can provide the elimination time, small amounts or traces of fentanyl can still remain in the body. So, although the elimination half-life might be 2-4 hours for IV fentanyl, it can take much longer for all traces of the drug to be completely eliminated. This is why fentanyl can still be detected in various tests depending on the type and sensitivity of the test.

How Long Does Fentanyl Stay In Urine?

Urine testing is one of the most common types of drug tests. The amount of time fentanyl stays in your urine depends on several factors, but generally, it ranges from 24 to 72 hours for the drug itself.

Fentanyl breaks down into metabolites, and one in particular, norfentanyl, can be detected in urine for a longer duration, sometimes up to 96 hours depending on the test’s sensitivity.

Various types of urine tests exist, and their detection window might differ. Standard immunoassay tests commonly used for drug screening may catch fentanyl for 24-72 hours, while more specialized tests like gas chromatography-mass spectrometry (GC-MS) can extend the detection window.

Other Types of Drug Tests

blood testing

IV Form: 20 hours
Oral Form: 3 days
Patches: 3.5 days

saliva testing

Fentanyl can be detected in saliva for up to 1-2 days after use.

Hair Testing

Fentanyl can be detected in hair for a longer period, possibly up to 90 days or more after use.

Quitting fentanyl can lead to withdrawal symptoms, emphasizing the addictive nature of the drug. Fentanyl withdrawal referes to the physiological and psychological symptoms that people experience when discontinuing fentanyl.

Fentanyl Withdrawal Symptoms

Navigating opioid withdrawal involves experiencing mild to severe symptoms that typically begin within 12-30 hours after the last dose. Common physical symptoms are:

  • Chills and goosebumps
  • Diarrhea
  • Nausea and vomiting
  • Muscle aches or fatigue
  • Insomnia and other sleep problems
  • Increased heart rate
  • Fever
  • Dilated pupils

Withdrawal also takes a toll on mental well-being. Anxiety, depression, and mood swings can be intense, and people may also experience difficulties in concentrating and losing interest in activities.

Fentanyl Withdrawal Timeline

Person With Anxiety

6 to 12 hours after last use
Early symptoms may include anxiety, restlessness, sweating.

Person With Insomnia

1-3 days after last use
Symptoms may include muscle aches, nausea, vomiting, diarrhea, chills, sweating, abdominal cramps, dilated pupils, and insomnia

Person With Late Withdrawal Symptoms

5-7 days after last use
Most acute symptoms subside within 5-7 days, although some discomfort may persist longer.

Person with Protracted Withdrawal

Some individuals may experience prolonged symptoms, known as post-acute withdrawal symptoms (PAWS), which may persist for weeks to months.

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The duration of fentanyl in the human body is influenced by several factors. Awareness of these factors, coupled with an understanding of the risks and consequences, is crucial for individuals and communities in helping people overcome fentanyl addiction.

Seeking professional help and fostering open conversations about fentanyl are vital steps in addressing the challenges posed by this drug. Treatment options include medical detox, medication-assisted therapy, counseling, and support groups.

If you or someone you know is struggling with fentanyl addiction or opioid abuse disorder, there is always help available. For Arizona residents, our Scottsdale addiction treatment centers are armed with addiction specialists who can help you get the support and treatment you need.

Don’t be afraid to ask for help. Reach out to us today and start embarking on a healing journey.