Following a report that Chicago warned about fentanyl-laced drugs at Lollapalooza, Johns Hopkins School of Medicine professor Dr. Marty Makary said on Friday that there is "virtually no safe drug."

"It's very hard to get the dose of fentanyl correct for recreational use. So it's very easy, given how potent it is to overdose. And fentanyl used to be in heroin, cocaine and in opioid pills that were used for drug use," Makary told "The Faulkner Focus."

"Now it's in virtually all drugs. It's in marijuana. So when people smoke marijuana thinking that it's safe, it may be laced with fentanyl. It's in methamphetamine." 

Makary reacted to Chicago public health officials advising Lollapalooza goers to test their drugs before partaking to make sure they are not laced with fentanyl. 

CHICAGO WARNS LOLLAPALOOZA-GOERS TO BE WARY OF FENTANYL: ‘TEST YOUR DRUGS’

The Chicago Department of Public Health put out a warning a day before the four-day music festival was set to begin in Grant Park. 

"ATTN Chicago & LOLLA FANS," a tweet from CDPH reads. "Fentanyl is a strong opioid that can easily cause overdose. Test your drugs before you use, carry Narcan, and don’t use alone. Call 911 if you suspect someone is overdosing." 

CDPH said fentanyl is found in cocaine, MDMA and other drugs – not just heroin. The department also said Narcan and fentanyl test strips can be picked up at Chicago public libraries "in easy-to-access Narcan dispenser kits."  

Narcan, also known as Naloxone, is a drug used to help to reverse symptoms of an overdose and save lives. 

Fentanyl is a synthetic opioid behind a massive spike in overdose deaths across the U.S. in recent years. Just a 2 mg dose is enough to kill a user with zero tolerance, whereas 60 mg of heroin is considered a lethal dose. 

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Makary said parents should understand that the only to avoid fentanyl is for children to avoid drugs altogether.

"It's at an endemic level. Even more children have died of drug use than have died of COVID in the last two years," he said, adding there is "no safe drug now with fentanyl."

Fox News' Bradford Betz contributed to this report.