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How Long Does Fentanyl Stay in Your System?

Medically Verified: 2/1/24

Medical Reviewer

Chief Editor

All of the information on this page has been reviewed and verified by a certified addiction professional.

Fentanyl is a synthetic opioid that is 50 times stronger than heroin and 100 times stronger than morphine, making it one of the most powerful opioid drugs on the planet. Because of its potency, fentanyl has been a primary driver of the opioid crisis in recent years. In 2020, synthetic opioids like fentanyl caused more than 56,000 overdose deaths.[1]

Fentanyl is especially dangerous when consumed unknowingly or when combined with other substances like opioids, benzodiazepines, or alcohol. If you have taken fentanyl, whether illicitly or as directed by a physician, it’s important to understand how long it stays in your system so you can avoid overdose as well as adverse side effects.

How Long Do The Effects of Fentanyl Last?

Fentanyl is sometimes prescribed to patients with chronic pain, particularly those battling cancer, in the form of a transdermal patch or a lozenge. The transdermal patch takes a few hours before it starts producing effects, but the effects of the lozenge occur rapidly. The effects from the patch can last up to 72 hours, while the effects of the lozenge can last for several hours depending on the dose.

Illicitly manufactured fentanyl (IMF) is fentanyl that is manufactured and sold on the streets. It usually comes in the form of a powder or is added to other substances. People may snort, smoke, or inject illicit fentanyl. The effects start to occur within seconds and can last for an hour or more.

Even though the effects of fentanyl wear off in the hours after taking the drug, it gets broken down into metabolites that stay in your system for much longer. As a result, a drug test can detect fentanyl in your system for several days after your last dose.

How is Fentanyl Metabolized?

Fentanyl is metabolized in the liver and excreted from the body through urine and feces.[2] Trace metabolites called norfentanyl may remain in the body and be detectable for several days after the last use of the drug.

In order to understand how long it takes your body to process and eliminate fentanyl, it’s important to understand the drug’s half-life. The half-life or elimination half-life refers to how long it takes half of a single dose of a substance to leave the body. It takes about 4-5 half-lives for a substance to leave your system.

The method in which fentanyl is administered can affect its half-life. When injected, fentanyl has a short half-life of 2-4 hours. This means if you inject fentanyl, it will be out of your system 11-22 hours after your last use.

The patch or the lozenge, on the other hand, have half-lives of 7-17 hours, meaning they will stay in your system for up to 36 hours.

Fentanyl Detection Times in Blood, Urine, Saliva, and Hair

As fentanyl is broken down by your liver, norfentanyl metabolites get left behind and are stored in various parts of the body.[3] This metabolite can be detected on drug tests to indicate fentanyl use. However, most standard drug tests only screen for morphine, and since fentanyl doesn’t metabolize into morphine, it’s unlikely a regular drug test will screen for fentanyl. Instead, an advanced drug test must be ordered.

Advanced drug tests can detect fentanyl in your system for several days, and, in some cases, even months. Estimated fentanyl detection times in blood, urine, saliva, and hair are:

  • Blood – up to 12 hours after the last use
  • Urine – between 8 and 24 hours after the last use
  • Saliva – between 1 and 3 days after the last use
  • Hair follicle – up to 90 days (3 months) after the last use

Factors That Affect Fentanyl Detection Times

There are many unique factors that influence how long fentanyl stays in your system as well as the rate at which it is metabolized. These include:

  • Dose – The higher the dose, the longer it will take your body to eliminate it.
  • Frequency and duration of use – The more you use fentanyl, the longer it will be detectable in your system.
  • Metabolism – People with fast metabolisms may process fentanyl faster than others.
  • Renal and liver function – Impaired kidneys or liver can slow down the metabolism of fentanyl.
  • Method of administration – Transdermal fentanyl will stay in your system longer than the lozenge or illicit fentanyl will.
  • Age – Older individuals tend to have a slower metabolism and will eliminate substances more slowly.
  • Weight and fat distribution – Drug metabolites are often stored in fat cells. The more fat cells a person has, the longer fentanyl may be detected in the body.

Drinking more water, getting plenty of exercise, and eating healthy may speed up your metabolism, but it is unlikely to flush substances like fentanyl out of your system any faster than they are already being eliminated. The only way to get it out of your system is to stop taking it and give your body time to process it.

Help for Fentanyl Abuse and Addiction

Fentanyl abuse is extremely dangerous. If you are abusing illicit fentanyl, it is only a matter of time before you become addicted or suffer from an overdose.

If you or a loved one are addicted to fentanyl, help is available. Our team at Carolina Center for Recovery offers individualized dual diagnosis treatment programs that are specified to meet your needs. Call now to learn more about our program or to begin your recovery journey.