How Long Does Fentanyl Stay in Your System?


Fentanyl stays in your system for hours to months, depending on the fentanyl dosage form and what is being tested. Drugs can remain 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 essential 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 synthetic opioid drug that is used in the treatment of short-term and long-term pain. The drug is potent.  Fentanyl is typically about 50 times stronger than heroin and 100 times stronger than morphine. It also takes the body longer to process and remove Fentanyl than other short-acting opioids. This combination can result in unwanted effects, like overdose.

Fentanyl is a significant driver of drug overdose deaths. If someone takes a potent dose, they could overdose. If someone takes more Fentanyl while their body still processes a previous amount, they could overdose. 

Overdose deaths from Fentanyl have skyrocketed, though. In 2014, fewer than 10,000 people died from synthetic opioids. In 2020, these drugs killed more than 56,000.

When misused, prescription fentanyl is dangerous. But most of the risk comes from illegally manufactured versions of the drug.

How Does Fentanyl Work?

Fentanyl works by attaching to the brain’s opioid receptors, like heroin or morphine. These areas in the brain control a person’s emotions and regulate pain. While Fentanyl interacts with these receptors, it causes the brain to release larger doses of dopamine. Dopamine comes from neurons within the brain’s reward center. The increase in dopamine is believed to be what causes the user to experience the euphoria of fentanyl high.

Fentanyl causes euphoria, but it can also cause the user’s breathing to slow down, increasing the risk that the person will experience an overdose. If this doesn’t occur and the person continues to ingest Fentanyl regularly, the brain will adapt to the presence of Fentanyl, so it won’t be as sensitive to the drug as it used to be. When this occurs, the user begins to lose the ability to feel pleasure from activities other than ingesting Fentanyl. This is known as “tolerance,” leading to fentanyl addiction.

What Are the Detection Times for Fentanyl, and What Affects Them?

The detection times for Fentanyl on drug tests differ. It will depend on the dose and the type of drug test (Hair, Blood, or urine sample). After you ingest Fentanyl, it will remain in your system based on the following factors:

Did you take other substances with Fentanyl?

If you use other substances at the same time that you are using Fentanyl, the different meanings will affect how your body metabolizes Fentanyl. The commonly mixed drugs with Fentanyl are cocaine, heroin, methamphetamine, or a prescription drug. Mixing Fentanyl with any other drugs is extremely dangerous and life-threatening.

How often do you use Fentanyl, and how long do you use it?

The length of time you use Fentanyl and how often you use it can cause the substance to remain in your system for longer. The longer you’ve been using Fentanyl, the longer it will stay in your system. Even long-term use of a fentanyl patch can remain in your system.

How did you use Fentanyl?

If you ingest Fentanyl intravenously, the substance will be eliminated faster than if you eat the drug by other methods. Oral and transdermal Fentanyl is also available.

How much did you take?

Taking a hefty dose of Fentanyl will remain in your system longer than a smaller one. Even if you’ve been taking Fentanyl for a short time but have taken too much, it will stay in your system.

Is your liver functioning properly?

If your liver is not functioning adequately, this will cause it to take a more extended period to metabolize Fentanyl. That’s why people who drug abuse Fentanyl and have liver diseases like cirrhosis will have Fentanyl in their system longer.

What about genetics?

Some people are unable to metabolize Fentanyl efficiently because of poor enzymatic function. The enzyme CYP3A4 does most of the work metabolizing Fentanyl.

What are your body mass index, body fat, and weight?

If you have more body fat than another user, your body will metabolize Fentanyl more slowly. Scientists believe this occurs because the body redistributes the Fentanyl to fat tissue.

What is your age?

If you are older, Fentanyl takes longer to be eliminated from the body than in a younger user. Age does affect how the body metabolizes Fentanyl.

In what ways can Fentanyl be absorbed through the body?

Fentanyl is a flexible and adaptable drug that is available in many forms. It can be absorbed readily through the stomach, bloodstream, and skin — as well as the mucous membranes in the mouth and nose.

A healthcare provider can prescribe Fentanyl as:

  • Pills
  • Shots
  • Patches 

Tablets on a s:

  • tick that is sucked on

Illegally made and sold Fentanyl can be:

  • Pills
  • Powders
  • Liquids on blotter paper, eye droppers, or nasal sprays

All of these forms make Fentanyl more dangerous. You may not even realize how much Fentanyl you take or if you are taking it.

How long does Fentanyl stay in your system?

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 form How long it lasts
Injectable (given in hospitals only) 30–60 minutes
Lozenge 4 hours
Intrabuccal tablet 4 hours
Sublingual tablet 2 hours
Sublingual spray 4 hours
Nasal spray 2 hours
Skin (transdermal) patch 72–96 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. A drug typically takes five half-lives to leave your system entirely. Therefore, half-lives can help you predict how long Fentanyl may stay in your body.

Fentanyl dosage form Half-life
Lozenge 3.2–6.4 hours
Intrabuccal tablet 2.6–11.7 hours
Sublingual tablet 5–13.5 hours
Sublingual spray 5.3–12 hours
Nasal spray 15–25 hours
Transdermal patch 20–27 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. Fentanyl is a synthetic or manufactured opioid with a 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 do 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, nor Fentanyl, can also be found in Urine simultaneously.

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?

Since Fentanyl stays 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.

What Happens if You Take Too Much?

The risk of overdose on Fentanyl is likely high because it is such a potent drug. The other reason many people overdose is that they are unaware they are taking Fentanyl, which has been laced with other substances.

For example, if you ingest Valium or Xanax with Fentanyl, the likelihood of an opioid overdose would increase significantly. It may even lead to respiratory depression, cardiac arrest, and the user’s death. Many people have died from overdoses, so you must call emergency services if you suspect someone is overdosing on Fentanyl.

A medical professional or an emergency technician can administer naloxone and methadone, a medication that can reverse the effects of a fentanyl overdose. It binds to the brain’s opioid receptors to block other opioids.

If a person experiencing a fentanyl overdose stops breathing, the naloxone can cause the person to start breathing again. If a person begins to overdose on Fentanyl, it’s doubtful they can administer naloxone alone.

That’s why it is recommended that friends or family members of someone experiencing an opioid use disorder keep naloxone where they can easily reach it and administer it in the event of an overdose. Naloxone comes as a nasal spray, lozenge, transdermal patch, or tablet, or you may inject it into the person’s vein, muscle, or under the skin.

How Can You Safely Stop Taking Fentanyl?

Fentanyl was classified under Schedule II of the Schedules for Controlled Substances Act. Using Fentanyl will likely lead the user to psychological or physical dependence.

Therefore, if you or your loved one are physically dependent upon Fentanyl, it isn’t safe to stop ingesting the substance. That’s because you will experience several unpleasant withdrawal symptoms, which may be particularly unbearable if you take large doses or use Fentanyl for a long time.

It will only take 12 hours after you ingest your last dose of Fentanyl for you to begin to feel the withdrawal symptoms. They can last for as long as seven days, but the first three days would be the hardest to endure.

Fentanyl withdrawal symptoms include the following:

  • Muscle pain
  • Chills
  • Weakness
  • Watery eyes
  • Runny nose
  • Diarrhea
  • Vomiting
  • Nausea
  • Increased heart rate
  • Hypertension
  • Difficulties sleeping
  • Loss of appetite
  • Depressive symptoms
  • Irritability


Fentanyl is a highly potent opioid with the power to trigger overdoses. Knowing how to responsibly use the drug and how long it stays in your system can increase your safety.

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