fentanyl detection time

Fentanyl is a powerful drug, but once the high wears off, it’s gone from your body. Right?


Fentanyl stays in the body long after its effects wear off. Even those whose last dose was weeks ago can be left worrying if their next drug screen will come back positive. Their job is on the line, and that fear can be overwhelming.

At San Antonio Recovery Center, when we say we’re a part of the community, these aren’t just words. Our staff reflects our diverse population, and we’re proud to be 65% Hispanic. As not just a treatment center but a public educator, we believe in providing vital information to anyone who needs it. Today, we’re going to be talking about how fentanyl affects your body, and how long it might stay in your system.

How Fentanyl Affects Your Body

Fentanyl is a prescription medication used to treat chronic and severe pain. It works by binding to the opioid receptors in your brain, essentially stopping any pain signals from transmitting. It can also lead to feelings of euphoria, sleepiness, and relaxation.

However, fentanyl also has several dangerous side effects: nausea, confusion, and respiratory failure. Fentanyl is 50 times more potent than heroin, so even small amounts can result in fentanyl overdose. Be extremely cautious whenever fentanyl is involved, whether recreationally or medicinally.

How Long Will Fentanyl Stay in Your System?

Fentanyl stays in your system long after its effects have worn off. It can be detected up to 72 hours after a single use, though for a majority of individuals it will be undetectable after the first 24 hours. The time after a dosage that fentanyl will still show up in the body is known as the “detection window”.

Its metabolites – leftover products created when your body breaks down a substance – can show up or far longer. One study found that even 96 hours after the last dose these metabolites could be detected.

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What Determines How Long Fentanyl Stays in Your System?

Several factors influence how long fentanyl will remain in your system.

  • Frequency of Use: Regular or chronic use of fentanyl will lead to accumulation in the body. This means that even after a period without using the substance, it can show up in your system. This is particularly true for hair follicle tests, which can detect use over long periods.
  • Dosage: Higher doses of fentanyl will take longer for your body to process and fully metabolize. Simply put, there is more fentanyl in your system, so your body will take longer to get rid of it. This should not be confused with building a tolerance, which is a different mechanism.
  • Individual Metabolism: Age, liver function, and metabolism all impact how quickly fentanyl is processed in the body. Body fat percentage and physical fitness can also play a role.

Different Ways Fentanyl Can Be Absorbed Through the Body

Fentanyl can be administered in various forms, each affecting its absorption and detection time. As a general rule, the faster fentanyl is absorbed, the more quickly it will be fully metabolized and out of your system.

  • Injection: This is the fastest method of absorption, as it puts fentanyl directly into the bloodstream. However, it will also have the shortest detection window.
  • Inhalation: Commonly done through nasal sprays, this is one of the fastest ways to administer fentanyl. It will typically have a slightly longer detection window than injection.
  • Oral: Oral administration is significantly slower than inhalation, as the fentanyl has to pass through the digestive system. This generally means that the detection window will be longer.
  • Transdermal: The slowest method of administration, fentanyl delivered through skin patches will typically last in the body longer than other methods.

Drug Tests and Fentanyl Detection

Fentanyl and its metabolites can remain in your body for days or even weeks after the last dose. There are three primary tests for fentanyl, each with its own degree of accuracy and detection window.

Blood Test

Blood tests are the most accurate form of test for fentanyl or its metabolites. This is because these tests measure the exact amount of the chemicals in your bloodstream. However, these tests can only detect fentanyl in a relatively short range of time, in roughly the last 24 to 48 hours.

Urine Test

Urine tests are the most common method of detection. These are fairly accurate, and can detect fentanyl far longer than blood tests. Urine tests for fentanyl may be clean after only 24 hours, but metabolites can be present more than 4 days (96 hours) after the last dose.

Hair Test

Hair follicle tests reach back even further. In many cases, these tests can detect fentanyl use for up to 90 days since the last dose. However, hair follicle tests mostly give positive results in cases of regular or frequent fentanyl use.

How Do I Get Fentanyl Out of My System Quickly?

The liver plays a key role in metabolizing substances in the body. While there is little you can do to speed this process up, there are several things to keep in mind.

Heavy drinking can slow down your liver’s ability to process fentanyl, keeping it in the body for longer. Malnourishment, dehydration, and a lack of sleep can influence how efficiently your liver is working. It’s important to stay rested, hydrated, and healthy.

However, there is no safe or effective way to “flush” the body, despite many rumors and home remedies claiming otherwise. The best way to get anything out of your system is to stop using it, stay healthy, and to wait for your body to fully metabolize the substance.

What Happens if You Take Too Much Fentanyl?

Taking too much fentanyl is always dangerous, and it remains one of the leading causes of overdose in the country. While any drug can lead to overdose, fentanyl’s potency makes it a particular risk, with only a few grams being lethal to most individuals. Symptoms can include severe vomiting, heart attacks, coma, and respiratory failure. If anyone taking fentanyl becomes unresponsive, seek immediate medical attention.

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Get Treatment for Fentanyl Addiction in San Antonio

If you’re ready to break free from your relationship with fentanyl, help and hope are available. Our fentanyl addiction treatment programs will guide you into the healthy and fulfilling life you deserve. Our extensive alumni network continues to walk by your side long after your treatment ends.

At San Antonio Recovery Center, we are with you for every step of your journey to reclaim your life. Our comprehensive programs provide the tools, support, and community you need. Call us today at 866-957-7885

Strength. Acceptance. Recovery. Community.

Now is the time to focus on your recovery.


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