About Fentanyl

Fentanyl, a synthetic opioid 50 times more potent than heroin and 100 times more potent than morphine, continues to drive overdose deaths in San Francisco and in cities across the nation.

An image of fentanyl and heroin side by side.

What is Fentanyl?

  • Fentanyl is a synthetic opioid that is 50-100 times stronger than morphine. Currently, illegally manufactured and unregulated fentanyl is driving overdose deaths in the United States, including in San Francisco
  • Legally produced fentanyl may be prescribed by a health care provider for the control of serious pain, and can be dangerous if not taken as prescribed. 
  • Fentanyl is cheap and may bd mixed into other drugs, such as heroin, cocaine, methamphetamine and MDMA. It has also been made into counterfeit pills.
  • When fentanyl is mixed into these other drugs, it can put people at even greater risk for overdose. 
  • Not all people are aware that fentanyl is present in their drugs, placing them at especially high risk of overdose. 

How can someone tell if fentanyl is present in their drugs?

It is not possible to determine whether fentanyl is present in illicit drugs by smell or taste. Also, the exact amount of fentanyl contained in any supply is often unknown. Because of fentanyl’s strength, even very small amounts of fentanyl can cause an overdose. 

Fentanyl test strips can help detect whether fentanyl is in a drug sample. These test strips can identify within 1-2 minutes if fentanyl is present. Test strips cannot tell how much fentanyl may be present, but they can often identify if fentanyl is present.

To get up to 10 fentanyl test strips, visit: 

Behavioral Health Services Pharmacy 
1st floor at 1380 Howard St 
San Francisco, CA 94103 

What are the effects of fentanyl?

Fentanyl, like other opioids such as prescription pain relievers and illicit opioids such as heroin, both relieves pain and can cause a person to experience a “high” or euphoria. However, opioids also produce ill effects, including physical dependence and addiction.

With regular use of fentanyl and other opioids, a person’s body can become physically dependent. This means that when a person suddenly stops using opioids, they will experience withdrawal symptoms, including body aches, shivers, nausea, vomiting, and diarrhea. These symptoms are treatable. 

Fentanyl and other opioids can also cause addiction, where a person, in addition to physical dependence, has craving for an opioid and continues to want to use in spite of negative effects. Addiction to fentanyl is treatable.    

Lastly, a person who uses fentanyl or another opioid regularly can become tolerant to its effects, meaning that a person will need to take more of the drug to feel the same effect. After some time, a person may no longer even feel the high or euphoria from the drug.

How does fentanyl cause an overdose?

Like other opioids, fentanyl slows a person’s breathing. At its most extreme, fentanyl stops a person’s breathing. If breathing is not restored, the lack of oxygen can be fatal.  

Fentanyl, a synthetic opioid 50 times more potent than heroin and 100 times more potent than morphine, continues to drive overdose deaths in San Francisco and in cities across the nation.

Can someone overdose on fentanyl by touching it?

No, it is not possible to overdose on fentanyl by touching it. 

What are risk factors for a fentanyl overdose?

Fentanyl acts quickly, but the risk of a fentanyl overdose depends on a number of factors, including the strength of the fentanyl and the amount taken, tolerance the person may have, and any alcohol or other drugs that may have been taken at the same time.  


The high potency of fentanyl means that even small amounts can cause an overdose.    

Other conditions can put someone at risk of a fentanyl overdose. These include use of drugs by oneself and use of multiple drugs at the same time. The risk of an overdose increases when fentanyl is used with drugs such as benzodiazepines (prescription medications for anxiety, such as Xanax or Ativan) and alcohol. 


Another risk factor for overdose is when someone stops using fentanyl and then starts using it again.  After a period of not using fentanyl, a person’s tolerance decreases. This loss of tolerance occurs in as little as a few days of no opioid use. If the person then uses after their tolerance has decreased, the same amount of fentanyl can potentially lead to an overdose.

What are the signs of fentanyl overdose?

A fentanyl overdose may result in decreased consciousness or complete unresponsiveness, cold and clammy skin, blue skin or lips, small pupils, and breathing that is very slow or has stopped.

Learn how to recognize and reverse an overdose via this SFDPH developed training series. 


Can naloxone (also known as Narcan) be used to reverse a fentanyl overdose?

Yes. When given correctly and quickly, naloxone can reverse a fentanyl overdose and can therefore be lifesaving.   

There are no known “naloxone-resistant” opioids. Fentanyl is no exception. When naloxone does not reverse a suspected opioid overdose, it may not be because the naloxone did not work. Instead, it may be because the naloxone was given too late or there were other, non-opioid drugs, that were consumed at the same time and led to the overdose.  

Naloxone should always be given when a drug overdose is suspected, even if the specific drugs used are not known. There are no risks of giving naloxone if opioids are not present. 

To get a free nasal Naloxone kit and training, visit: 

Behavioral Health Services Pharmacy 
1st floor at 1380 Howard St 
San Francisco, CA 94103 

What happens when someone who regularly uses fentanyl stops using it?

Most people who use fentanyl daily will develop physical dependence to fentanyl and will experience withdrawal symptoms if they stop using it suddenly. These withdrawal symptoms can be very severe and include severe body aches, sweating, anxiety, diarrhea, nausea, vomiting, and strong cravings for opioids. Withdrawal symptoms can start within hours and can last for days.

Can fentanyl addiction be treated?

A person who has a fentanyl addiction can be effectively treated.   

The most effective treatment for opioid addiction include medications. There are three FDA-approved medications for the treatment of fentanyl addiction; methadone and buprenorphine are the most effective and have been shown to save lives.

  • Methadone activates the same opioid receptors as fentanyl. It is an oral medication that that reduces or eliminates cravings for other opioids, and reduces risk of overdose. l It can only be dispensed from specialized opioid treatment programs.   

  • Buprenorphine also activates the same opioid receptors as fentanyl to ease withdrawal symptoms and cravings. It is available as an oral medication (tablet or film) or as a monthly injection . Unlike methadone, it can be prescribed in primary care settings and dispensed from retail pharmacies.   

  • Naltrexone blocks the opioid receptor, therefore preventing fentanyl from activating it. It is given as a monthly injection.   

Methadone and buprenorphine reduce the risk of dying by up to 50%. 

These medications may be combined with behavioral therapies, which can also be effective in treating people with an addiction to fentanyl and other opioids. Examples of behavioral therapies include:  

  • Cognitive behavioral therapy: Helps people learn and modify their drug use behaviors and helps them effectively manage triggers and stress.  

  • Contingency management: Motivates people to reduce their use of different drugs by providing tangible incentives or “rewards”. Contingency management is the most effective treatment for people with addiction to stimulants, such as methamphetamine or cocaine.  

These behavioral treatment approaches are effective, especially when used with medications. Learn about our substance use disorder treatment services

Video: Protect yourself from the dangers of fentanyl

Watch this video from the CDC to learn more about fentanyl. 



Last updated August 23, 2023