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Heroin vs. Fentanyl: Which is Stronger?

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The recent increase in overdose and addiction is primarily centered around opioids. A surge in the illegal trafficking of opioids to the United States has increased the availability of drugs like heroin. Both heroin and the synthetic opioid fentanyl have been involved in thousands of opioid overdoses in the last several years. In high doses, opioids can be fatal, but which drug is stronger? Learn more about morphine fentanyl and their respective strengths.

What is Heroin?

Heroin is a semi-synthetic opioid that’s made from morphine, a natural chemical that’s found in opium poppy plants. Heroin was used once for medicinal purposes in the United States, but it has since been replaced by other opioids. Like other opioids, it can cause pain relief and sedation by binding to opioid receptors in the body. These receptors are responsible for managing your body’s pain response. Heroin can also cause potent euphoria and deep relaxation. It’s a popular recreational drug, but frequent use can lead to chemical dependency and addiction. 

Pure heroin in appropriate doses can cause constipation and chemical dependence. However, illicit heroin is unpredictable and may contain adulterants that weaken it. When users grow accustomed to weak heroin and then gain access to a purer supply, they may take a dose that’s too high. Heavy doses can lead to a fatal overdose in which breathing slows down to the point of oxygen deprivation. 

What is Fentanyl?

Fentanyl is a synthetic opioid used in medical settings and battlefield medicine as a treatment for moderate to severe pain. However, it’s also produced in clandestine laboratories and smuggled into the United States as a recreational drug. It works in a way that’s similar to heroin and other opioids. It binds to opioid receptors and activates them, causing pain relief, sedation, and euphoric effects. As a synthetic drug, it can be made without the use of a natural opiate-like morphine. It’s cheaper and easier to make and move than heroin and other prescription opioids, so dealers often mix it into heroin to increase profits. Like other opioids, fentanyl can cause respiratory depression and fatal overdoses.

Which is Stronger?

Fentanyl can be lethal to the average person in doses as small as three milligrams. That’s about the same weight as a single snowflake. By comparison, the average lethal dose of heroin is 30 milligrams. According to the U.S. Drug Enforcement Administration (DEA), fentanyl is between 80 and 100 times more potent than morphine. It’s around ten to 50 times more potent than heroin. Because it’s so potent, fentanyl can be shipped in smaller packages than heroin, which makes it cheaper and easier to smuggle. 

It’s often added to heroin to encourage the perception that the heroin supply is of higher quality because of its strength. Fentanyl is also a cheap way to mask heroin that’s been weakened through adulteration. However, people that take heroin that has fentanyl mixed into it are at a greater risk of an overdose. 


Bond, A. (2016, September 30). This photo shows exactly why Fentanyl is deadlier than heroin. from

CDC. (2019, May 31). Fentanyl. from

DEA. (n.d.). Fentanyl. from

National Institute on Drug Abuse. (n.d.). Opioids. from

National Institute on Drug Abuse. (2019, November). Heroin. from

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