Patrick Slattery Fentanyl September 1, 2025 If you’ve ever taken fentanyl or another strong opioid, you know that the side effects can be intense. As time goes on, and you develop a fentanyl use disorder, those side effects often get more severe. The side effects of fentanyl addiction include a combination of short-term and long-term symptoms, ranging from mild digestive issues to a potentially deadly overdose. These side effects have a serious impact on your overall health and can affect all different parts of your life. In fact, fentanyl is one of the most dangerous substances used recreationally. Fentanyl was found to be the cause of death for 2,020 Floridians in the first half of 2024. That was the most out of any psychoactive substance. At Real Recovery, we know firsthand how severe the side effects of fentanyl are. Many of us are in recovery ourselves, and we’re here to support you through your journey. Recognizing Fentanyl Side Effects The side effects of fentanyl are typically broken down into two categories. Short-term side effects of fentanyl occur directly after you’ve taken opioids. Many of these “side effects” are the reason that you might choose to take opioids recreationally. These side effects will fade as fentanyl makes its way out of your system. Long-term side effects develop after a period of extended fentanyl consumption. However, these symptoms tend to be more pervasive and last even after you’re no longer “high” on fentanyl or other opioids. Both long-term and short-term side effects can have a serious impact on your mental and physical health. Common Short-Term Side Effects of Taking Fentanyl Not everyone experiences all of the possible short-term side effects of consuming fentanyl. The individual side effects you experience may vary depending on your age, weight, gender, dosage, metabolism, or other factors. Some of the most common short-term side effects of taking fentanyl include: Confusion Drowsiness Weakness Euphoria Pain relief Nausea and vomiting Headaches Dizziness Low blood pressure Slow breathing Cramps and indigestion Constipation Poor balance Slurred speech Small pupils When you take a powerful opioid, like fentanyl, you may “nod” in and out of consciousness. Among people who take opioids recreationally, this is often called “being on the nod,” because your head will droop and shoot back up as you fight to remain awake. Long-Term Side Effects Associated with Fentanyl Addiction Repeated fentanyl use can have a serious impact on your body and mind over the long term. When you enter recovery and stop taking fentanyl and other opioids, most of these side effects can be eliminated, but the process will take time. 5 common long-term symptoms of continued fentanyl consumption are: Mood instability Lowered sex drive Changes in the menstrual cycle Respiratory problems Low immunity/frequent illness The longer you take fentanyl, the higher your tolerance will become. This means you will need more and more of the substance to feel the same effects. This can quickly develop into a fentanyl use disorder. While a fentanyl use disorder is most common among people who use the substance recreationally, it can also occur if you have a prescription. Can Fentanyl Cause Hallucinations? Yes, in more extreme cases, fentanyl and other opioids can cause hallucinations. Although these are not particularly common side effects, they can be very frightening when they occur. These hallucinations are often described as “waking dreams” and tend to be visual or auditory in nature. In most cases, hallucinations are associated with high doses of fentanyl. Anecdotal evidence suggests that people with a higher tolerance for fentanyl are less likely to experience hallucinations. If you, or someone you know, takes fentanyl recreationally, you may intentionally seek out the hallucinations that the substance can trigger. Other times, hallucinations occur as a result of a therapeutic dose of fentanyl, although this is less common. Understanding the Side Effects of Fentanyl Withdrawal When you take an opioid like fentanyl for an extended period of time, your body adjusts to having opioids in your system. This is what leads to a physical dependence on the substance. When you stop taking fentanyl after developing a physical dependence, you’ll experience withdrawal symptoms. This can happen even if you’re taking fentanyl as prescribed by a doctor. Most fentanyl withdrawal symptoms mimic those of the flu. While these symptoms aren’t typically dangerous, they are very uncomfortable. Symptoms of withdrawal from fentanyl and other opioids include: Abdominal pain Fast heart rate Excessive yawning Goose pimples Insomnia Tremor Dilated (enlarged) pupils Watery eyes Nausea and vomiting Diarrhea Muscle cramps During withdrawal, you’re also likely to experience emotional side effects, including feelings of anxiety or depression. Another major feature of fentanyl withdrawal is the cravings for more opioids. Withdrawal side effects can start as early as 8 to 24 hours after your last dose. Acute withdrawal symptoms typically last for about 10 days. Post-acute withdrawal syndrome (PAWS) can last for months or longer. However, the symptoms of PAWS are more psychological, and they tend to come and go in waves. These negative symptoms, along with the intense cravings for fentanyl, are a major contributor to the development of fentanyl use disorder. Many people end up taking more of an opioid just to avoid withdrawal symptoms. The Danger of Potential Fentanyl Overdose Fentanyl is widely considered the strongest opioid, both in terms of illegal and prescription use. For context, reports from the Drug Enforcement Administration (DEA) suggest that the substance is as much as 50 times more potent than heroin and 100 times more potent than morphine. Because fentanyl is so strong, overdose is a major concern. An overdose happens any time you take more of a substance than your body can handle. An overdose can happen the first time you take fentanyl or the 100th. Overdose is most common among people who don’t have a tolerance for fentanyl, as well as people who return to their usual dose after losing their tolerance due to abstaining from the substance. Opioids significantly slow down your central nervous system and other bodily functions. When an overdose happens, bodily functions can slow severely or stop. The “opioid overdose triad” looks like: Falling in and out of consciousness (nodding) Slowed or stopped breathing Extremely small or pinpoint pupils Other symptoms that are common during a fentanyl overdose include: Limpness Blue tint to the skin, especially the mouth and nails Choking or gurgling sounds Cold skin Slow heart rate A fentanyl overdose is extremely dangerous and can result in permanent disability or death. If you’re with someone, and you’re concerned that they could be overdosing, call 911 immediately. Florida’s Good Samaritan Law prevents you from being charged for having or taking illegal fentanyl when you’re calling for help. If you have it available, you should administer naloxone, which can reverse the effects of an opioid overdose, while you wait for help to arrive. You can get free naloxone mailed to you through the Florida Harm Reduction Collective. They partner with a distribution organization that provides free naloxone training videos as well. Fentanyl Prescriptions vs. Illicit Fentanyl Consumption: Are the Side Effects Different? If you take prescription fentanyl as directed by your doctor, you’re far less likely to experience long-term side effects than if you’re taking the substance illicitly. However, you may still experience the same short-term side effects caused by fentanyl consumption. If you’re experiencing side effects while taking prescription fentanyl, it’s important to talk to your doctor immediately about how it’s affecting you and what alternatives are available to you. Although it’s rarer, fentanyl use disorder can still occur even if you’re taking fentanyl under the supervision of a doctor. Severe side effects, particularly long-term side effects, are more likely to occur if you’re taking fentanyl recreationally. The best way to avoid side effects is to end your fentanyl use entirely. Get Treatment for Fentanyl Addiction at Real Recovery in Tampa, Florida No matter how you started taking fentanyl, the side effects of fentanyl use disorder can have a profound impact on your life. They can complicate your relationships, damage your health, and create a vicious cycle that’s difficult to break out of. Thankfully, you don’t have to figure it out on your own. High-quality treatment for fentanyl addiction will empower you to change your life for the better. Your care plan should be tailored to meet your specific needs. However, a good treatment program will include a combination of 12-step programming, proven therapeutic techniques, and extensive opportunities for support from other people in recovery. At Real Recovery, we understand that healing from a fentanyl use disorder is about more than just sobriety. That’s why we’ll help you get access to additional resources, including gym memberships, SNAP benefits, educational opportunities, and more. Give us a call at 813-373-6762. Real people. Real solutions. Real results. - Share on Facebook Share on twitter