• Posted June 15, 2026

Fentanyl Users Take Daily Doses 60 Times The Lethal Level

People who use illicit fentanyl build up a mind-boggling tolerance to the drug, eventually taking massive doses that would kill others, a new study finds.

The findings mean fentanyl could be much more challenging to quit than previously assumed. 

The average fentanyl user in Los Angeles takes a daily amount that is roughly 60 times that of the 2-milligram dose that could kill someone who’s never used opioids, researchers report in the journal Drug and Alcohol Dependence.

Overall, users consume daily fentanyl doses that are equal to nearly 9,000 milligrams of morphine, researchers found.

“We find that people are regularly exposed to doses of opioids that would have seemed impossible to me before I started this work,” senior researcher Chelsea Shover said in a news release. She’s an associate professor-in-residence of medicine at the University of California, Los Angeles.

Such doses could make it difficult to counter fentanyl addiction using standard medications for opioid use disorder, researchers noted.

As a fully synthetic drug, fentanyl can be produced more easily and cheaply than heroin, researchers noted. It also has a potency that is far higher than heroin or oxycodone, which can lead users to overdose by taking more than they intended.

For the study, researchers aimed to quantify users’ exposure to street fentanyl using morphine milligram equivalence (MME), a standardized measure that allows comparison between different types of opioids.

The team analyzed the purity of more than 500 fentanyl samples tested between September 2023 and January 2026 by Drug Checking Los Angeles, a community-based drug testing program.

Researchers also asked 47 fentanyl users about how much they took in a day, and how they used the drug.

“We had been treating illicit-opioid doses as a black box — an unknowable, a curiosity,” lead investigator Morgan Godvin, project director at Drug Checking Los Angeles, said in a news release.

“If at the molecular level, fentanyl is fentanyl, we should be able to quantify exposure, so we decided to estimate it with the Drug Checking Los Angeles data,” Godvin said. “The results surprised us all.”

Results showed that users were taking every day an average amount of fentanyl equivalent to 8,887 milligrams of morphine.

They can withstand that dose because a tolerance develops, not just to the drug’s intoxicating effects, but also to the respiratory effects that lead to overdose, Shover said.

“To put it in perspective, in the hospital settings, fentanyl is often dosed in 100 microgram vials,” Shover said. “One gram of average purity fentanyl that we tested had a dose equivalent to more than that 1,200 of these vials. So people are getting daily doses that are on par with injecting hundreds of the hospital vials or taking 440 Percocet pills.”

These levels can make it incredibly difficult for a user to stop taking fentanyl, because addiction medicines like methadone, buprenorphine and naltrexone are not geared to helping users cope with withdrawal from such heavy daily doses, researchers said.

“Of course, starting medications for opioid use disorder is going to be harder for fentanyl than it is for heroin,” Shover said.

These results provide addiction experts with the information they need to help fentanyl users successfully confront their opioid use disorder, researchers said.

“It’s no longer, ‘how do we treat someone who smokes a gram of fentanyl per day,’ it’s ‘how do we treat someone using thousands of MMEs of oral morphine in fentanyl per day?’ That question and its answers feel more accessible, less abstract to clinicians,” Shover said.

More information

The National Institute on Drug Abuse has more about fentanyl.

SOURCE: UCLA, news release, June 10, 2026