Fentanyl Side Effects and Addiction Signs

Fentanyl, a synthetic opioid, is about 100 times more potent than morphine. Because of its high potency, fentanyl is one of the most dangerous and deadliest opioids in existence.1 Fentanyl is primary prescribed to manage severe pain in those with serious medical conditions like cancer or for those who are tolerant to other opioids, but it is often misused and abused for its powerful effects. Fentanyl is also illegally made in clandestine labs and is often added to heroin and other substances, unbeknownst to the user.1,2

When pharmaceutical fentanyl is taken as directed, it can be safe and therapeutic, but when it is misused or bought on the streets, it becomes more dangerous, increasing the risk of harmful side effects, addiction, overdose, and death.

In this article: 

Short-Term Side Effects of Fentanyl Use

Even if you are taking fentanyl exactly as prescribed by your doctor, you may experience fentanyl side effects, but misusing or abusing fentanyl increases the likelihood and potential severity of these short-term effects. Other factors that may affect potential side effects include:

  • Dose
  • Length of fentanyl use
  • Method of administration (patch vs. injecting)
  • Individual physiology
  • Whether you’ve used other opioids before
  • Whether you are mixing fentanyl with other substances

Some common short-term side effects of fentanyl use include:2,3

  • Drowsiness
  • Dizziness
  • Sedation
  • Nausea or vomiting
  • Difficulty urinating
  • Pupillary constriction
  • Slowed breathing rate
  • Anxiety or depression
  • Insomnia
  • Back or chest pain
  • Tremors or shaking
  • Reddening of the neck, face, or upper chest

Some fentanyl side effects can be dangerous. Call your doctor or 911 immediately if you experience any of the following severe side effects:3

  • Hallucinations
  • Agitation
  • Severe muscle twitching or stiffness
  • Loss of coordination
  • Rapid heartbeat
  • Confusion
  • Seizures
  • Hives
  • Rash

Those who use patches will have additional fentanyl patch side effects like rashes around the area where the patch attaches to the skin. However, many of those who misuse fentanyl don’t wear the patch. Instead, they remove the liquid from the patch and inject it directly. Others who don’t inject the drug may choose to suck the liquid or gel from the patch.4

Long-Term Side Effects

Chronic fentanyl use, misuse, or abuse can lead to harmful long-term side effects, such as:5,6

  • Enhanced sensitivity to pain
  • Infertility
  • Sexual dysfunction
  • Liver damage
  • Severe constipation
  • Depression
  • Suicidal ideation or attempts
  • Sleep-disordered breathing (e.g. sleep apnea)
  • Increased risk of heart attack or heart failure
  • Increased risk of falls and fractures (particularly in elderly patients)
  • Physiological dependence, meaning you’ll experience fentanyl withdrawal symptoms when you suddenly quit
  • Tolerance, or requiring more fentanyl to experience the desired effects

People who inject fentanyl may be at risk for additional long-term consequences, such as:6

  • Abscesses
  • Puncture marks
  • Scars
  • Cellulitis
  • Peripheral edema (swelling of legs or hands)
  • Track lines
  • Bacterial endocarditis (infection of the heart lining)
  • Contracting HIV or hepatitis
  • Tuberculosis

Although not synonymous with addiction, dependence can contribute to the development of addiction. If you are dependent and you abruptly quit using fentanyl, you will experience unpleasant and distressing withdrawal symptoms. Taking fentanyl will then alleviate these withdrawal symptoms. This pattern of abstinence and return to use can ultimately create a cycle of problematic fentanyl use that can be difficult to stop. Fentanyl addiction is characterized by compulsive fentanyl use despite negative consequences you may experience.6 It’s important to know the signs of fentanyl addiction so you can get help for yourself or someone else.

Signs of Fentanyl Addiction

If you are struggling with a fentanyl addiction, also known as an opioid use disorder, you may find that it’s challenging to stop using fentanyl on your own. Some common signs of a fentanyl addiction include:6,8

  • Experiencing strong cravings for fentanyl
  • Using fentanyl despite interfering work, social, or home obligations
  • Using fentanyl despite negative physical or psychological consequences
  • Failing to abstain despite efforts to do so
  • Spending an excessive amount of time obtaining or using fentanyl
  • Avoiding previously enjoyable activities in favor of fentanyl use
  • Using fentanyl in dangerous situations, such as while driving
  • Mixing fentanyl with other substances, such as alcohol
  • Requiring higher doses to feel effects
  • Requiring fentanyl in order to avoid withdrawal symptoms

Fentanyl Withdrawal Symptoms

If you abruptly quit or reduce your fentanyl use, you may experience the following withdrawal symptoms:6,8

  • Insomnia
  • Excessive yawning
  • Fever and sweating
  • Goose bumps
  • Nausea and vomiting
  • Diarrhea
  • Muscle aches
  • Depressive mood
  • Anxiety
  • Rapid heartbeat
  • Runny nose
  • Teary eyes

Although fentanyl withdrawal is not typically life-threatening, it can be extremely painful, which is why detox programs can be beneficial. A staff of medical professionals will provide you with medical care and oversight to ensure your comfort throughout withdrawal. Call 800-934-1582(Who Answers?) to speak to a treatment support specialist about finding an opioid detox program that is right for you.

Fentanyl Overdose and Death

All opioids can be deadly, especially if misused or abused, but fentanyl, in particular, has an extremely high overdose risk and has been a major contributor to the opioid overdose crisis. This is because it is far more potent than other opioids, such as morphine or even heroin. Even relatively small doses of fentanyl can lead to an overdose.

Signs of a fentanyl overdose include:2,3

  • Stupor
  • Unresponsiveness
  • Clammy, cold skin
  • Blue skin
  • Pinpoint pupils
  • Slow, shallow breathing or stopped breathing
  • Coma

If you suspect you or someone else has overdosed on fentanyl or any other drug, call 911 immediately and stay with the person. Provide as much useful information to the operator as possible, including:

  • What drug was taken
  • How much of the drug was taken
  • Whether it was mixed with other substances
  • When the last dose was taken

Naloxone is an opioid overdose medication that reverses the life-threatening effects of an opioid overdose. It is available over the counter in many states, or you can get a prescription from a doctor. If you or someone you know uses fentanyl or any other opioids, it’s a good idea to purchase naloxone and keep it on you in the event of an emergency. If you recognize symptoms of a fentanyl overdose in yourself or someone else, give the first dose of the naloxone then call 911. Multiple doses may be necessary to reverse the effects.3

Fentanyl Addiction Treatment

If you or someone you care about is addicted to fentanyl, help is available. Fentanyl addiction treatment programs occur on an inpatient or outpatient basis and vary considerably in treatment philosophy, amenities, and features. But every program provides therapy and counseling to help explore the reasons for substance use, replace maladaptive behaviors with healthy, drug-free behaviors, and teach effective coping mechanisms and relapse-prevention strategies.

Inpatient fentanyl addiction programs require that you reside at the recovery center for the duration of treatment, whereas you will attend outpatient programs during the day then return home in the evening. Inpatient treatment programs are often beneficial for individuals who want to jumpstart their recovery in a drug-free setting, away from triggers, such as friends or family members who use drugs.

Conversely, outpatient may be a good choice for individuals who want to continue working or attending school while recovering from fentanyl addiction. These types of programs, given the freedom, require a bit more motivation to quit using fentanyl. Additionally, outpatient programs may be used as step-down care after you’ve already completed an inpatient program, as they provide structure and therapy in a less intensive environment.

What Happens After Treatment?

Addiction recovery doesn’t happen overnight. Rather, it is a lifelong process. Rehab provides you with the foundation for sobriety but it’s extremely important to build upon the skills you learned in rehab. After you complete a fentanyl addiction treatment program, it’s important to receive ongoing support in the form of aftercare. Aftercare can occur in many settings, including:

  • Sober living homes
  • 12-step groups, such as Narcotics Anonymous
  • Non-12-step groups, such as SMART Recovery
  • Step-down care (outpatient rehab)
  • Individual therapy or group counseling


  1. Drummer, O. (2018). Fatalities caused by novel opioids: a review. Forensic Sciences Research, 4(2), 95-110.
  2. Drug Enforcement Administration. (2021). Drug Fact Sheet: Fentanyl.
  3. U.S. National Library of Medicine. (2021, January). Fentanyl. MedlinePlus.
  4. Guan, W., Schneider, R., & Patterson, J. (2011). “I am in pain!” a case report of illicit use of transdermal fentanyl patches. The Primary Care Companion for CNS Disorders. 13(5).
  5. Baldini, A., Von Korff, M., Lin, E. H. B. (2012). A Review of Potential Adverse Effects of Long-Term Opioid Therapy: A Practitioner’s Guide. The Primary Care Companion for CNS Disorders, 14(3).
  6. American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). American Psychiatric Publishing.
  7. Sinha, R. (2011). New findings on biological factors predicting addiction relapse vulnerability. Current Psychiatry Reports, 13(5), 398-405.
  8. Azadfard, M. (2020). Opioid Addiction. StatPearls Publishing.
  9. National Institute on Drug Abuse. (2021). Opioid Overdose Crisis.
  10. Kassani, A., Niazi, M., Hassanzadeh, J., & Menati, R. (2015). Survival analysis of drug abuse relapse in addiction treatment centers. International Journal of High Risk Behaviors and Addiction. 4(3): e23402.

the Take-Away

Fentanyl, a synthetic opioid, is about 100 times more potent than morphine. Because of its high potency, fentanyl is one of the most dangerous and deadliest opioids in existence.1 Fentanyl is primary prescribed to manage severe pain in those with serious medical conditions like cancer or for those who are tolerant to other opioids, but …