Part of the complete guide to understanding addiction
Table of Contents
- How long does fentanyl stay in your system?
- How long does fentanyl stay in urine?
- How long does fentanyl stay in the blood?
- How long does fentanyl stay in your hair?
- Will fentanyl show up in a drug test?
- Fentanyl half life chart
- What influences fentanyl’s half life?
- Fentanyl withdrawal timeline
How Long Does Fentanyl Stay In Your System?
Many wonder about how long fentanyl stays in your system; they worry about illegal fentanyl use being detected via a drug test. But before discussing how long it stays in the system, let’s get clear on what fentanyl is.
What is Fentanyl?
Fentanyl is a powerful painkiller, between 50 and 100 times more effective than morphine. It is often given to patients post-surgery but has become increasingly popular as a recreational drug, despite becoming illegal due to its addictive properties and high overdose risk.
How Does Fentanyl Work?
Fentanyl is a synthetic opioid which blocks pain signals, increases dopamine levels in the brain and causes profound feelings of euphoria and relaxation. These feelings are what make fentanyl so addictive. The lethal dose of fentanyl can be tiny, causing many tragedies.
Half-life of Fentanyl
The best way to calculate the answer to how long does fentanyl stay in your system is by determining its half-life.
Elimination half life refers to how long it will take for half of a single dose of any drug to be eliminated from the body. This includes fentanyl and other opiate pain relievers.
The exact half life of fentanyl is going to vary based on the method that it is administered. When a patient takes fentanyl intravenously, its half life will be between two to four hours. This results in it taking between 11 to 22 hours before all traces of the medication are out of his system. If one takes more fentanyl in that time, then the half life will restart.
Fentanyl is also available in a lozenge or a patch. This method takes longer to leave the system because it releases very slowly into the body. It is estimated that the half life of this type of fentanyl will be between 7 to 17 hours. This translates into 36 hours before the drug leaves your system completely.
While the actual substance may be out of your system within this time, patients who take fentanyl should be aware that fentanyl will leave behind small traces known as metabolites. These metabolites linger in the body far past the half-life. One of these metabolites is called Norfentanyl, and people often ask “how long does Norfentanyl stay in your system?” While a simple drug test will not detect these metabolites, a thorough drug test may pick up these fentanyl traces even several days later.
How Long Does Fentanyl Stay In Urine?
Fentanyl can be easily detected in urine for 24 to 72 hours via an advanced urine drug test1. If it has been more than 72 hours since one took fentanyl, it will not show up in an advanced urine test, and it may be flushed out of the system as soon as 24 hours after taking Fentanyl.
However, even after the body has metabolized the Fentanyl completely, the metabolite Norfentanyl may still be detectable up until 48 to 96 hours after administration of the initial dose of Fentanyl. 
Additionally, long-term fentanyl users may have Fentanyl stored in their fat, 2 which can greatly extend the period of time in which the drug can be detected in a urinalysis. In consistent users, Fentanyl may be detected for 7 days and Norfentanyl for 13 days. There have even been reports of Norfentanyl being detected for as long as 26 days after the final dose of fentanyl was administered.
How Long Does Fentanyl Stay in the Blood?
Blood tests are another method of detecting drug use in individuals. This is considered a highly ineffective method of testing, because fentanyl will not last in the blood for more than 12 hours. Other organs in the body will absorb the substance, which means that fentanyl can still be in the body without being in the blood. An individual will need to have taken the substance right before the drug test for it to show up in the blood.
How Long Does Fentanyl Stay in Your Hair?
An advanced hair drug test may be one of the most effective and accurate methods of determining whether an individual has used fentanyl in the last few months. Since hair grows relatively slowly, it will provide an accurate health history timeline that cannot be gained via any other method. It is possible to detect fentanyl in the hair for about three months after last use. A post-op patient who was given fentanyl may have the drug show up in the hair up to three months later.
However, it is difficult to calculate exactly how long ago the fentanyl was used. Unless it shows up in the hair follicles in very large amounts, it may not be basis enough to prove that the patient has recently used it.
Will Fentanyl Show Up In a Drug Test?
While fentanyl is a strong opiate, it is not often tested for on a standard drug test. Standard drug tests are meant to detect common opioids that will metabolize and turn into morphine. Since fentanyl does not metabolize into morphine, it is unlikely to show up unless an advanced drug test is ordered.
However, it is always wise to be prepared for an advanced drug test in the event it is ordered. There is no last-minute solution when you’re wondering how to get fentanyl out of your system. Knowing the illegal fentanyl drug timeline will help you prepare yourself accordingly.
Fentanyl can be detected in the urine, hair, and blood for a number of hours and even days after the final use. Neither fentanyl nor its metabolites can be detected consistently in saliva, and it is therefore not considered a viable testing method . In short:
- Blood: Up to 12 hours
- Urine: 24 to 72 hours (Longer for heavy users)
- Hair: Up to 90 days
- Saliva: Not viable
If you have been given fentanyl after surgery at any time within the past few months and will undergo a drug test, be sure to disclose this information so that any detection of fentanyl is not held against you.
Fentanyl Half Life Chart
|Fentanyl Half Life||Casual User||Long Term User|
|Fentanyl in Urine||24 – 72 Hours||7 – 19 Days|
|Norfentanyl in Urine||48 – 96 Hours||7 – 26 Days|
|Fentanyl in Blood||12 Hours||12 Hours|
|Fentanyl in Hair||Up to 90 Days||Up to 90 Days|
|Fentanyl in Saliva||Not viable||Not viable|
What Influences the Half Life of Fentanyl?
The half life of fentanyl in your body, and therefore the exact amount of time it takes to be flushed from the body, will depend on a number of factors which vary from individual to individual. Three large factors are weight, height, and body mass. The heavier or taller the individual, the less likely it is that the fentanyl will show up. Age plays a significant role as well, since younger people are better able to metabolize any substance as compared to seniors.
Another factor would be genetics. Some find that they are able to metabolize substances faster than others, while some find that substances stay in their body longer. Things like hepatic function, food intake at time of drug use, and metabolic rate, will all influence the speed at which one can get fentanyl out the system.
Other factors include:
- Urinary pH of the individual
- Drug dosage
- Method of drug administration
- Frequency of use
- Length of use
- Simultaneous use of other drugs
How Long Does Fentanyl Withdrawal Take?
Understanding how long fentanyl stays in your system may give an idea of the length of fentanyl withdrawal symptoms. A withdrawal can be both lengthy and painful; one may experience dizziness, confusion, sleepiness, weakness, and even coma and unconsciousness if they used for a long time. Withdrawal is best done beneath professional medical supervision, in a safe and controlled environment.
Fentanyl leaves the system over 11 to 22 hours when administered intravenously, and in up to 72 hours when taken as a lozenge or transdermal patch. Withdrawal symptoms usually will not turn severe until after this time. As the body begins to sense the absence of the substance and must function without it, withdrawal symptoms may turn severe. One should expect another three to five days of detox-related discomfort before they begin to feel better. The substance may already be out of their system, but the body has to learn how to function again without the addictive substance.
Fully recovering from a Fentanyl addiction requires a course of treatment in an inpatient drug rehab. Reach out today! Our trained admissions professionals are standing by, ready to help you find your way back home. Contact Avenues Recovery.
To broaden your knowledge of fentanyl addiction, including discovering whether touching fentanyl can hurt you, browse our online resources.