Fentanyl Side Effects & Health Risks

Fentanyl is a powerful synthetic opioid that can pose numerous negative short- and long-term health effects and risks.¹ People who use illicit fentanyl, or know someone who does, should be aware of these risks and understand how fentanyl can impact their health and well-being. This article will help you understand the risks of using fentanyl and how to find treatment for fentanyl addiction.

What Are the Possible Side Effects of Using Illicit Fentanyl?

Fentanyl is 50-100 times stronger than morphine.¹ This high level of potency can result in numerous and potentially severe fentanyl side effects.¹

Like other opioids, fentanyl can cause euphoria, which may encourage people to keep using it.² Chronic opioid use can lead to dependence as well as addiction, which is diagnosed as an opioid use disorder (OUD).² People who use opioids can also experience a potential opioid overdose, which could be lethal, and use of fentanyl increases the risk of overdose due to its potency.²  

Fentanyl effects can depend on the dose and whether a person concurrently uses other substances.² Side effects of fentanyl may include:¹

• Euphoria.
• Drowsiness.
• Nausea.
• Confusion.
• Sedation.
• Constipation.
• Problems breathing.
• Unconsciousness.

Long-Term Risks of Fentanyl

As mentioned above, ongoing use of opioids including fentanyl can result in opioid use disorder (OUD), which is a chronic medical condition that results in compulsive opioid use despite significant and debilitating negative consequences.² It can also result in physiological dependence, which is an adaptation that a person’s body makes due to chronic administration of a substance. ^{2, 3} Oftentimes dependence is accompanied by an associated withdrawal syndrome.^{2, 3} Dependence is not addiction, but it is often present in people who are addicted to fentanyl and is a notable diagnostic criterion for an opioid use disorder.^{2, 3}

Only a medical professional can diagnose OUD, but understanding the diagnostic criteria for OUD can help you know when it might be time to seek treatment. The criteria involve: ²

• Using opioids in larger amounts or over a longer period than was intended.
• A persistent desire or repeated efforts to control or cut down opioid use.
• Spending a lot of time in activities necessary to obtain, use, or recover from opioids.
• Cravings, or a strong desire to use opioids.
• Failing to fulfill major obligations at work, school, or home due to opioid use.
• Continuing to use opioids despite persistent or recurrent social or interpersonal problems caused or exacerbated by the effects of opioids.
• Giving up or reducing important social, occupational, or recreational activities because of opioid use.
• Using opioids in situations where it is physically hazardous to do so (such as driving or operating machinery).
• Continuing opioid use despite knowledge of having a persistent or recurrent physical or psychological problem that is likely to have been caused or exacerbated by opioids.
• Tolerance, meaning a person needs increased amounts of opioids to achieve intoxication or they do not experience the same effects with the same doses.
• Withdrawal when opioid use is cut back or stopped.

Risks & Dangers of Unintentional Fentanyl Use

Unbeknownst to the user, fentanyl can be present in different street drugs.¹ Street drugs such as heroin, cocaine, methamphetamine, counterfeit pills (e.g., opioids and benzodiazepines like Xanax) and MDMA, may be cut with fentanyl due to unintentional contamination or intentional contamination due to the drug’s inexpensive price and its ability to increase the potency of the substance.¹ However, using fentanyl with other substances can significantly increase the risk of overdose.¹

People who use street drugs should be aware of the increased risk of overdose due to fentanyl use.^{1, 4} Using fentanyl test strips can be an effective harm reduction method that can help to determine whether a substance has been contaminated with fentanyl.⁴ Test strips are an inexpensive and potentially life-saving tool that can detect the presence of fentanyl within minutes.⁴

Fentanyl Overdose Risks

The potential for overdose is present regardless of whether a person uses fentanyl alone or with other substances.¹ However, as mentioned above, people who use street drugs may not realize that they could be using drugs that are mixed with fentanyl.⁴ This can greatly increase the risk of overdose, especially for users with a low opioid tolerance, as they can be using a drug that is much stronger than their bodies are accustomed to.¹

An opioid overdose is a medical emergency that can be fatal, especially if people do not receive prompt medical attention.¹ According to the Centers for Disease Control and Prevention, the rates of overdose deaths involving synthetic opioids other than methadone, which includes fentanyl and fentanyl analogs, increased by over 22% from 2020 to 2021.⁵ More than 150 people die every day from overdose related to synthetic opioids like fentanyl.^{4 fentanyl and overdose}

The symptoms of a fentanyl/opioid overdose can include:^{4, 8}

• Unconsciousness or an inability to awaken.
• Slow or shallow breathing.
• Bluish lips or fingernails.
• Pinpoint pupils that don’t react to light.

If you suspect that someone is overdosing, you should immediately call 911.¹ You should also administer naloxone (Narcan, Kloxxado) while waiting for emergency services to arrive and stay with the person until EMS arrives.⁴ Naloxone is an opioid overdose reversal medication that can rapidly restore a person’s breathing.⁶ However, people still need to receive emergency attention and monitoring to ensure that their breathing doesn’t stop, and sometimes people may require multiple doses of naloxone from overdose due to strong opioids like fentanyl.¹

Finding Treatment for Fentanyl Misuse and Addiction

If you or a loved one are struggling with fentanyl misuse and addiction, it’s important to seek help to prevent the negative consequences and risks. Effective treatment can help people stop using fentanyl and regain control of their lives.⁷

The first step might be to consult your doctor to have an evaluation, discuss drug addiction treatment options, and ask for referrals. You can also use our fentanyl support directory to search thousands of rehabs across the country. Or call our free, confidential helpline at to speak to an understanding and knowledgeable admissions navigator, who can answer any questions you may have, help you understand your rehab options, and verify your insurance benefits.