How Long Does Fentanyl Stay in Your System

How Long Does Fentanyl Stay in Your System?

Fentanyl is a potent synthetic opioid that doctors prescribe to treat moderate to severe and chronic pain. Usually, fentanyl is only prescribed when a patient is tolerant of lesser opioids. Fentanyl is 50 to 100 times stronger than morphine. 

Fentanyl can cause side effects like euphoria, drowsiness, and relaxation. These effects of fentanyl can be incredibly addictive, causing you to repeatedly abuse fentanyl despite the negative effects. The only way to recover from an addiction to fentanyl is to attend a professional drug rehab program. 

How long fentanyl remains in your body depends on a variety of factors, including the method of administration you use. IV fentanyl can stay in your system for 22 hours, while patches or lozenges take 36 hours to leave your body.

What is the Half-Life of Fentanyl?

When you are discussing how long a substance stays in your body, the half-life is important. A drug’s half-life displays how long it takes your body to eliminate half of a substance. It typically takes 4 to 5 half-lives for your body to completely flush out a drug. 

The half-life of fentanyl depends on how you are using it. When fentanyl is injected, its half-life is between 2 to 4 hours. This means it could take up to 22 hours for your body to eliminate fentanyl. 

If you are using fentanyl transdermal patches or lozenges from a doctor, the half-life is between 7 and 17 hours, so the body might not eliminate fentanyl for 36 hours after your last dose.

You should never take more fentanyl before you are directed to do so by your physician. Doing so could cause a life-threatening respiratory depression and overdose.

Factors that Affect How Long Fentanyl Stays in Your System

There are a variety of factors that can influence how long fentanyl stays in your system. For example, if you have been using it long-term, you might have it in your system longer than a first-time user. 

Other factors that can affect how long fentanyl stays in your body include:

  • Method of administration (i.e., smoking, snorting, injecting, and more)
  • Frequency and duration of use
  • The amount of fentanyl you consume
  • The rate of your metabolism
  • Age and weight
  • Body fat percentage 
  • Genetics and biological sex 
  • Water and nutrition intake 
  • The health of your liver and kidney 
  • Overall health
  • Whether you’ve consumed other substances like alcohol or prescription medications 

Fentanyl comes in multiple forms, including liquid, patches, lozenges, and powder. The type of fentanyl you are consuming can also affect how long it stays in your system. 

How Long Can Drug Tests Detect Fentanyl?

Fentanyl can be detected in urine, blood, saliva, and hair follicles. The window of detection depends on the type of test being used. For example, fentanyl is detectable longer on a hair test than urine testing. 


Urine tests are the most common type of drug test used. This is generally because they are affordable and the least invasive method of drug testing. These tests can detect fentanyl in urine for 24 to 72 hours after your last dose. 

If you have been using fentanyl long-term, you might test positive longer than someone who has only used fentanyl one time. Typically, this occurs because the fentanyl misuse causes it to build up in your body over time. 


Saliva tests are not used as frequently as urine tests because they offer a shorter window of detection. They are often used by police officers to determine if you are driving under the influence of a drug like meth or cocaine. Unfortunately, saliva tests tend to be unreliable when it comes to testing for fentanyl. 


Healthcare professionals often use blood tests to find out if there is a drug in your bloodstream. Most substances flush out of your blood faster than other areas of your body like urine. Blood tests can usually detect fentanyl for 5 to 48 hours after your last dose. 


Hair tests are not commonly used for a couple of reasons. First, they are expensive to send off to the lab to be analyzed. Additionally, studies have found them unreliable because they may discriminate based on things like hair color. 

Hair tests can find any substance in your hair follicles for up to 90 days after your last dose. 

Find Help for Fentanyl Abuse and Addiction

If you or a loved one suffers from fentanyl addiction, it’s time to seek help. Being addicted to fentanyl puts you at a significant risk of experiencing a fatal overdose. Thankfully, addiction treatment programs can help you recover from addiction and achieve long-term sobriety.
At Living Room New Jersey, we can help you overcome an opioid use disorder. Contact us today for more information on our fentanyl addiction treatment programs.

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