How Long Does Prescription Fentanyl Stay In Your System? Plus, 4 More FAQs

Fentanyl is an opioid medication that treats severe pain. But the potent substance can be incredibly dangerous, especially if prescription fentanyl is used incorrectly or if you consume illegally made fentanyl. One major risk is overdose. In 2022, 75% of overdose deaths in the U.S. involved illegally made fentanyl.

If you’re using a prescription fentanyl product, knowing how long fentanyl stays in your system can help you avoid fentanyl risks. We’ll cover the answer to this question and other frequently asked questions below.

1. How long does fentanyl stay in your system?

How long fentanyl lasts in your system depends on which fentanyl product you’re prescribed. There are a few different products, including a fentanyl injection (Sublimaze) that’s sometimes used in the hospital for pain or anesthesia. For home use, three products exist:

• Skin patch

• Dissolvable tablet (Fentora)

• Lozenge (Actiq)

After taking the skin patch off, fentanyl can last up to 5 days in your system. The dissolvable tablet (which dissolves against the lining of your cheeks) can last about a day in your system. And the lozenge (which dissolves on your tongue) can last 1 to 2 days in your body.

The majority of research on how long fentanyl lasts in the body has been done on people who took a single dose of fentanyl (or just a few doses). But most people who are prescribed fentanyl will typically be on this medication for longer. So this research doesn’t accurately reflect the way prescription fentanyl is used in the general population. 

If you take prescription fentanyl regularly, you can assume that there’s some level of fentanyl in your system at all times. This may make you feel drowsy, dizzy, and nauseated. It can also interact with other medications or alcohol. You should avoid activities that require alertness until you know exactly how fentanyl affects you.

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One reason that long-term fentanyl use can keep fentanyl in your body for many weeks is because fentanyl is “lipophilic,” or fat-soluble. This means that fentanyl can enter fat cells in the body and build up in these cells, causing it to stick around longer.

Good to know: There’s also very little research looking at how long illegally made fentanyl lasts in the body in people who use it regularly. One small study looked at 12 people with opioid use disorder using illegally made fentanyl. Fentanyl stayed in the urine of some participants for a week or longer. In fact, one person tested positive for fentanyl for almost 3 weeks after their last dose.

2. What factors affect how long fentanyl stays in your system?

A few factors can affect how well fentanyl is absorbed in the body and how long it lasts. These factors may be important to know about if you’re relying on prescription fentanyl to treat severe pain, such as cancer pain. Knowing about these factors can also help you avoid risks.

Some factors to consider include:

• Specific fentanyl product: As discussed above, the fentanyl from the skin patch typically lasts longer in the body than prescription oral forms.

• Age: As we age, our body composition and organ function changes. As a result of this, some medications may have more intense effects in older adults. You may need a lower fentanyl dosage if you are 65 years old or older.

• Liver function: Fentanyl is broken down (metabolized) in the liver. If you have liver disease, you may need a lower dose of fentanyl to prevent it from building up in your body and leading to dangerous side effects.

• Kidney function: Fentanyl leaves the body through the urine. If you have kidney disease, you may need a lower dose of fentanyl.

• Other medications you take: Many medications can interact with fentanyl. Some of these interactions cause fentanyl to build up in the body, and other interactions cause decreased levels of fentanyl. It’s best to avoid medications that interact with fentanyl entirely if possible. If you can't, your healthcare professional (HCP) may adjust your fentanyl dose.

3. What are the risks of fentanyl?

Prescription fentanyl can help treat severe pain in people who don’t find relief from other medications. But because fentanyl has serious risks, it’s only prescribed when absolutely necessary. One scenario where fentanyl may be used is to help with cancer pain.

Even when prescription fentanyl is used correctly, fentanyl has side effects. These include:

• Nausea

• Constipation

• Drowsiness

• Dizziness

• Low blood pressure

• Lack of energy

• Mood changes

However, fentanyl has more serious risks. These include:

• Increased sensitivity to pain

• Severely low blood pressure

• Slowed breathing

• Dependence and misuse

• Opioid use disorder

• Overdose

Part of the reason fentanyl can be so dangerous is because it’s extremely potent. For example, it’s up to 100 times more potent than morphine. Serious fentanyl risks are most likely if prescription fentanyl is used differently than how it’s prescribed, or if a person is using illegally made fentanyl. To drastically reduce your risk of fentanyl side effects, don’t use more prescription fentanyl than what’s prescribed to you. You shouldn’t take extra doses, or use it for longer than your HCP instructed. And avoid illegally made fentanyl at all costs by avoiding illegal drugs entirely.

Keep in mind: If you or a loved one takes fentanyl, it’s a good idea to carry naloxone (Narcan, Zimhi) on you at all times. This life-saving medication can quickly reverse the effects of an opioid overdose. You can get naloxone without a prescription, and it’s even available over-the-counter as of 2023. To learn how to use it, read instructions on how to administer naloxone in another GoodRx article. 

4. What’s the difference between prescription fentanyl and illegally made fentanyl?

When used correctly, prescription fentanyl is less dangerous than illegally made fentanyl. There are a few reasons that using illegally made fentanyl is life-threatening, including:

• Illegally made fentanyl may be combined with other dangerous substances. Other illegal substances may be mixed in with illegal fentanyl. This includes heroin, methamphetamine, and cocaine. On their own, these products can be life-threatening. When combined with fentanyl, the risk of overdose and death skyrockets.

• You may be using more fentanyl than you think. Since illegal drugs aren’t regulated, there’s no way to know how much fentanyl is in any given product. You may be using significantly more fentanyl than you think, increasing your risk of overdose and death.

• Illegally made fentanyl may be more addicting. Because illegal fentanyl can be combined with other addictive substances that cause a “high,” you may be more likely to misuse it and develop opioid use disorder, slowed breathing, or overdose.

It’s worth noting that any illegal drug use is dangerous. It’s becoming more common for fentanyl to be added to a wide range of illegal drugs, so you may consume fentanyl without knowing. And you can’t tell if a product has fentanyl in it just by seeing, smelling, or tasting it. This is incredibly dangerous, especially for people who don’t regularly use opioids. A substance as strong as fentanyl could quickly cause an overdose. Even small doses of fentanyl could have this effect.

5. What are the signs of fentanyl misuse and what should you do?

Using prescription fentanyl correctly doesn’t typically result in misuse or opioid use disorder. But if you use fentanyl differently than how it’s prescribed, or if you use illegally made fentanyl, your risk is much higher.

Fentanyl misuse includes taking more fentanyl than what’s prescribed, or using it for longer than prescribed. Signs that misuse has developed into an opioid use disorder include:

• Difficulty or inability to cut back on opioid use

• Having trouble completing your daily tasks due to opioid use

• Having cravings for opioids

• Spending a lot of time getting or using opioids

• Disengaging from social activities due to opioid use

• Continuing to take opioids even though it’s causing relationship problems

If you notice you’ve developed any of these patterns, reach out to your HCP immediately. They can help evaluate you for opioid use disorder, and provide guidance on how to proceed. You may need treatment, which often includes therapy and medications. Support groups like Narcotics Anonymous or SMART Recovery can also help.

Good to know: If you see a friend or family member struggle with opioid use, show compassion and talk to them about your concerns. For tips on how to approach them and offer support, head to our GoodRx article on best ways to help someone with opioid use disorder. 

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Written by:

Amy B. Gragnolati, PharmD, BCPS

Amy Gragnolati, PharmD, BCPS, is a pharmacy editor for GoodRx. Amy currently holds her pharmacist license in Georgia and California.

Reviewed by:

Christina Palmer, MD

Christina Palmer, MD, is a board-certified family physician with a focus on chronic care management, women’s health, and mental health. She’s the co-author of “Open Heart: When Open-Heart Surgery Becomes Your Best Option.”.

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