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How Much Fentanyl Can Kill You? What Is a Lethal Dose?

Peter Manza, PhD profile image
Reviewed By Peter Manza, PhD • Updated Oct 2, 2023 • 7 cited sources

Experts say about 2 mg of fentanyl is a lethal dose for most people.[1] This drug is 50 to 100 times stronger than morphine.[2] It doesn’t take very much of the substance to overwhelm your central nervous system and cause an overdose. 

A 2 mg dose of fentanyl is about the size of 15 grains of table salt.[2] It’s small enough to fit on the tip of a pencil and far too tiny for you to spot when it’s mixed into a pill or powder. 

If you’re accustomed to misusing fentanyl, you may be able to tolerate a dose that would kill other people. But since drug dealers don’t always have robust quality control measures, you won’t know if the next dose contains much more than 2 mg of fentanyl.

How Many Deaths Does Fentanyl Cause?

Years ago, illicit drugs like heroin and painkillers like OxyContin grabbed overdose headlines. That changed around 2013, when illicit fentanyl entered the black market.[3] Now, more people are dying of fentanyl than ever before, including people who never intended to take the drug. 

Between 2015 and 2016, overdose deaths caused by fentanyl doubled from 3.1 to 6.2 deaths per 100,000 people. Researchers noticed, as it meant fentanyl death rates were larger than those attributed to heroin during the same period.[3]

Between June 2019 and 2020, an estimated 48,000 out of 83,335 overdose deaths were caused by fentanyl.[4] Researchers say the death rate increased more than 29-fold since 2012.[4]

How Much Fentanyl Is Too Much?

While researchers say that 2 mg is a fatal dose, the facts are complicated.[1] Some people can take more of this drug and survive. Others can overdose on much smaller amounts. 

Your opioid exposure is one of the most important factors in drug tolerance. Drugs like fentanyl, oxycodone and heroin change brain chemistry, leading to tolerance with repeated use.[5] People with opioid tolerance need bigger doses to achieve the same effect. Smaller doses just don’t affect them in the same way over time. 

Someone accustomed to large Vicodin doses may tolerate more fentanyl than someone who has never used opioids. The longer a drug habit and the higher the doses, the bigger the tolerance.

Other factors that could influence how much fentanyl could kill you include the following:[6]

  • Age: Older people with underlying organ health issues may process drugs slower than younger people. Smaller doses have a bigger effect on them.
  • Sex: Body composition (including water retention, body fat, muscle mass and size) can influence how quickly drugs move through your body. Smaller individuals generally feel greater effects from smaller doses.
  • Genetics: People with more drug receptors may process drugs quicker than those with fewer. 
  • Health: Poor organ health or underlying medical conditions could lower your tolerance for drugs. If you take the same dose as someone without health issues, it’s likely that you will feel much stronger effects. 

How Is Fentanyl Sold?

Dealers often mix tiny amounts of fentanyl into their products. Almost anything you buy could contain fentanyl, and you may never know it. 

Some dealers mix fentanyl into counterfeit pills that look like oxycodone and Adderall. If you buy pills from dealers, not licensed pharmacies, your dose could contain fentanyl.[7]

Dealers also mix fentanyl into illicit drugs, including the following:[7]

  • Cocaine
  • Methamphetamine 
  • Heroin

You can’t see, smell or taste fentanyl.[7] It’s impossible to know if the drug you’re about to take is contaminated without a drug test. The longer you use drugs bought from dealers, the higher your risk of exposure and potential overdose. 

While you can use fentanyl test strips to determine if fentanyl is present in the batch of drugs you bought, and you should take this harm reduction measure, it isn’t a surefire way to detect fentanyl. It’s possible that fentanyl is not present in the tiny bit of the batch you tested, but it is present elsewhere in the batch. If you buy drugs on the street, there is no foolproof way to ensure fentanyl is not present. 

Reviewed By Peter Manza, PhD

Peter Manza, PhD received his BA in Psychology and Biology from the University of Rochester and his PhD in Integrative Neuroscience at Stony Brook University. He is currently working as a research scientist in Washington, DC. His research focuses on the role ... Read More

  1. Facts about fentanyl. United States Drug Enforcement Administration. Published April 2021. Accessed August 21, 2023.
  2. Fentanyl: One pill kills. Texas Department of Health and Human Services. Accessed August 21, 2023. 
  3. Zoorob M. Fentanyl shock: The changing geography of overdose in the United States. International Journal of Drug Policy. 2019;70:40-46.
  4. Volkow ND. The epidemic of fentanyl misuse and overdoses: challenges and strategies. World Psychiatry. 2021;20(2):195-196. doi:10.1002/wps.20846 
  5. Opioid addiction. U.S. National Library of Medicine. Published November 1, 2017. Accessed August 21, 2023.
  6. Johnson-Davis K. Pharmacokinetics. Association for Diagnostics and Laboratory Medicine. Published January 19, 2021. Accessed August 21, 2023.
  7. Dose of reality: Get the facts on opioids. Wisconsin Department of Health Services. Published August 11, 2023. Accessed August 21, 2023. 

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