What is the Strongest Opioid?

Last Updated: November 3, 2023

Editorial Policy | Research Policy

Knowing the strengths of different opioids can help you gauge your risk of addiction, abuse and dependence when taking these drugs.

If you take opioids, you may wonder how strong your medication is compared to other opioids. Potency can vary widely from one opioid to another, and some can be significantly stronger or weaker than others. Knowing the strength of your opioid and understanding its Controlled Substance Schedule can help you gauge your risk for opioid abuse, addiction and dependence.

Opioid Addiction and Abuse

Opioid addiction is an issue throughout many parts of the United States. Up to 12% of people who take opioids for chronic pain go on to develop an opioid addiction, and almost 50,000 Americans died from opioid overdoses in 2019 alone.

Risk factors for opioid abuse include:

  • Abuse of other substances
  • Untreated mental health problems
  • Younger age
  • Having a social or family environment that encourages drug abuse

Signs of addiction may first be noticed by close friends or family. While many signs of addiction are nonspecific, it is important to be aware of them because they can indicate someone may be struggling with substances. Signs include:

  • Having problems with work or school
  • Trouble keeping up with commitments and responsibilities
  • Mood changes
  • Spending time with new friends to the exclusion of old ones
  • Changes in sleep habits
  • Legal problems

Why Are Opioids Addictive?

Opioids are addictive because they trigger the brain’s reward circuit. When a person takes an opioid, they often experience feelings of intense relaxation or euphoria. The brain’s reward circuit stimulates the person to keep seeking out the drug in an attempt to experience the pleasurable feelings again.

Over time, a person can develop opioid tolerance and dependence. Tolerance means that the person will need increasingly higher doses to achieve the same effects as before. Dependence means that the body becomes used to the drug’s presence, and stopping the drug can lead to withdrawal symptoms. Together, tolerance and dependence can create a cycle of repeated opioid use, causing a person to become addicted.

List of Opioids Strongest to Weakest

Most opioids are compared to the injectable form of morphine when it comes to measuring strength. The morphine milligram equivalent (MME) of opioids is a widely used metric that can help you and your doctor determine how strong your opioid regimen is. However, several factors can influence opioid conversion charts and change how an opioid affects you. These include:

  • Your opioid tolerance: You will likely build up a tolerance if you take opioids over the long term, meaning you must take higher doses to feel the same effects. However, taking one opioid does not always mean that you will be tolerant of another opioid. This phenomenon, known as incomplete cross-tolerance, means that you may need to reduce the dose of a new opioid to avoid an overdose.
  • The way you are taking the opioid: Opioid conversion calculations are specific to the medication’s route of administration. For example, injectable oxymorphone is ten times stronger than morphine, while oral oxymorphone is about three times as strong as morphine.
  • Your physiology: Many opioids are broken down by the liver. In some cases, your genetics can mean that opioids may be stronger or weaker than expected. For example, codeine may be weaker or stronger than expected in a person who carries mutations in the CYP2D6 gene.


Carfentanil is currently the strongest opioid available. It is a Schedule II controlled substance that is 10,000 times stronger than morphine and 100 times stronger than fentanyl. The drug is not intended for use in humans. Instead, it is used as a tranquilizer for elephants and other large animals. Synthetic (or man-made) opioids like carfentanil were responsible for almost 73% of opioid overdose deaths in 2019.


Fentanyl is a Schedule II opioid that is one of the strongest narcotics available to manage pain. Injectable fentanyl is 100 times more potentthan morphine, while transdermal fentanyl is 50 times more potent than morphine. Even an amount of fentanyl the size of a grain of sand — approximately two millimeters — can be deadly. From 2020 to 2021, synthetic opioids like fentanyl caused a 55.6% increase in opioid overdose deaths.

Oxymorphone (Opana)

Oxymorphone Is a Schedule II opioid used for pain. Injectable oxymorphone is 10 times stronger than morphine, while oral oxymorphone is three times as strong as morphine.

Hydromorphone (Dilaudid)

Hydromorphone Is a Schedule II opioid prescribed for pain. Injectable hydromorphone is about 6.6 times stronger than morphine, while oral hydromorphone is around four times stronger than morphine.


Buprenorphine is a Schedule II opioid that is about five times stronger than morphine. However, buprenorphine overdose deaths are rare. This is because the drug only partially activates opioid receptors in the central nervous system, meaning that there is a limited risk of overdose. The drug is most often prescribed as medication-assisted treatment (MAT) for those trying to quit other opioids.


Heroin is a Schedule I opioid that is two to three times stronger than morphine. It is a drug of abuse that has no acceptable medical uses. It takes about 200 mg of heroin to cause an overdose in someone who has never taken opioids before. However, those who struggle with heroin may be able to tolerate up to two grams of the drug. In 2019, more than 14,000 people died from heroin overdoses in the United States, accounting for almost one-third of opioid deaths that year.


Methadone is a Schedule II opioid used for pain and MAT. Injectable methadone is about twice as strong as morphine, and oral methadone is about as strong as morphine when methadone treatment first begins. However, taking high doses of methadone over longer periods of time can affect the relative potency of morphine.

Oxycodone (Percocet, Oxycontin, Roxicodone)

Oxycodone Is a Schedule II opioid that is about 1.5 times as strong as morphine. One formulation of oxycodone — the long-acting opioid Oxycontin — is widely blamed for helping to kickstart the opioid epidemic. The drug is used to treat pain.

Hydrocodone (Vicodin, Lortab)

Hydrocodone is a Schedule II opioid that is about as strong as morphine. It is used to treat pain. Hydrocodone-containing drugs are the top-selling opioids in the United States, accounting for more than 30.3 million prescriptions in 2019 alone.


Codeine is an opioid that is around 85% weaker than morphine. The drug’s schedule ranges from II to V and depends on the formulation being prescribed. The drug is prescribed for both pain and cough.

Tramadol (Ultram)

Hydrocodone is a Schedule IV opioid that is roughly 10 times weaker than morphine. Tramadol is the second most commonly prescribed opioid in the United States, with almost 20 million prescriptions dispensed in 2019. It is prescribed for pain.

Demerol (Meperidine)

Meperidine is a Schedule II opioid that is roughly 10 times weaker than morphine. It is prescribed for pain. However, the drug is rarely prescribed nowadays because it carries a higher risk of seizure compared to alternative opioids.

Opioid Addiction Treatment

Seeking help for an opioid addiction can seem overwhelming at first. The first step should always be to seek the advice of a doctor, as quitting opioids cold turkey can be uncomfortable or dangerous.

The Recovery Village Cherry Hill at Cooper provides comprehensive opioid addiction treatment, ranging from medical detox to rehab and aftercare. Our large, 55,000-square-foot facility has 90 beds and offers a variety of amenities, including:

  • Fully-equipped gym
  • Indoor basketball half-court
  • Outdoor volleyball court
  • Yoga room
  • Game room
  • Entertainment lounges
  • Outdoor bocce ball
  • Outdoor shuffleboard

If you or someone you love is struggling with opioid abuse and addiction, The Recovery Village Cherry Hill at Cooper can help. Contact us today to speak with a caring intake expert and learn about treatment programs that can work well for your situation.


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Drug Enforcement Administration. “Controlled Substances.” November 18, 2021. Accessed February 14, 2022.

Centers for Disease Control and Prevention. “Synthetic Opioid Overdose Data.” March 25, 2021. Accessed February 14, 2022.

Drug Enforcement Administration. “Facts About Fentanyl.” Accessed February 14, 2022.

Centers for Disease Control and Prevention. “Heroin Overdose Data.” March 25, 2021. Accessed February 14, 2022.

European Monitoring Centre for Drugs and Drug Addiction. “Heroin Drug Profile.” Accessed February 14, 2022.

Pratt, Victoria M.; Scott, Stuart A.; Pirmohamed, Munir; et al. “Codeine Therapy and CYP2D6 Genotype.” Medical Genetics Summaries, March 30, 2021. Accessed February 14, 2022.

Wightman, Rachel S.; Perrone, Jeanmarie; Scagos, Rachel; et al. “Opioid Overdose Deaths with Buprenorphin[…]trospective Analysis.” Journal of Medical Toxicology, January 2021. Accessed February 14, 2022.

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GlobalRPH. “Opioid Conversion Calculator Morphine Eq[…]valents – Advanced.” Accessed February 14, 2022.

ClinCalc. “Acetaminophen; Hydrocodone.” Accessed February 14, 2022.

Utah Department of Health Medicaid. “Opioid Oral Morphine Milligram Equivalen[…]) Conversion Factors.” Accessed February 14, 2022.

Hagmeyer, Kathleen O.; Mauro, Laurie S.; Mauro, Vincent F. “Meperidine-Related Seizures Associated w[…]lled Analgesia Pumps.” Annals of Pharmacotherapy, January 1, 1993. Accessed February 14, 2022.

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National Institute on Drug Abuse. “Opioid Overdose Crisis.” March 11, 2021. Accessed February 14, 2022.

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