A 29-year-old mental health worker in Brooklyn sometimes spends his weeknights singing at karaoke dive bars with friends, where he snorts cocaine before singing.

His drug behavior used to be more uninhibited, but reports of rising overdoses — not from the cocaine itself but from fentanyl, a synthetic opioid that dealers mix in — has led him to take extra precautions before partying. Before going out, he empties his cocaine into another receptacle, and checks the bag for traces of fentanyl using a test strip he purchased online.

“If people ask for some, it feels good to be able to confidently say, ‘Yep, this has been tested,’” said the mental health worker, who spoke on the condition of anonymity because he could lose his job.

Cocaine use has always involved a certain level of danger: it is against the law, highly addictive and has many health risks. But some cocaine users in New York City — whom this reporter met through harm reduction activists, community organizers and mutual acquaintances — say that the fear of fentanyl has made them wary of using any cocaine that has not been tested.

Dozens of bars, clubs and restaurants in New York City have started to offer fentanyl test strips, including All Night Skate in Brooklyn, Rise Radio Cafe in East Williamsburg and Nowadays, a nightclub in Ridgewood, Queens that offers test strips behind the bar.

“It was a no-brainer for us,” said Marcus Tirado, the owner of Viva Birria, a taco restaurant on the Lower East Side that began stocking strips this spring, after two acquaintances died from fentanyl-adulterated cocaine. “When we first put them out, we had customers say, ‘What is that?’ They were like, ‘Let me get one for my friend,’” Mr Tirado said. “It’s catching on.”

Viva Birria received the strips from the A$AP Foundation, a harm-reduction group named for the hip-hop artist A$AP Yams, which distributes them throughout the city including the Perrotin gallery on the Lower East Side, the International Bar in the East Village, and Guevara’s in Brooklyn.

Some older clubgoers say they are not only concerned about their own health, but the safety of their friends. “In this environment of fentanyl, it’s a whole different ballgame, compared to when I started going to parties 27 years ago,” said a 43-year-old tech company manager from Brooklyn. She said she methodically tests her stash before going out, using strips she bought from DanceSafe, a nonprofit group.

Concern among cocaine users has grown so pervasive that some drug dealers now advertise their product as pre-tested and send photos of negative results. “We’re not going to stop people from doing drugs,” said a former drug dealer who , until recently, lived in Brooklyn. He said he stared testing his product after his girlfriend’s fentanyl scare in 2018. “The best we can do,” he added, is “help them do it safely and responsibly.”

Fentanyl strips have even become a provocative party favor. Dirty magazine, which bills itself as “New York’s horniest fashion publication,” passed out 250 test strips at a party last December at the ClockWork Cros gallery on Canal Street, and thousands more at other events.

“It takes a real cultural ubiquity to normalize them,” said Ripley Soprano, 30, the magazine’s editor in chief. “Integrating the strips fully into our scenes by having them readily available is really the only way to make an impact.”

Deaths from drug overdoses reached record levels in 2021, mostly from the rise in fentanyl, according to preliminary data from the Centers for Disease Control and Prevention. Of the 108,000 overdose deaths last year, about 71,000 involved fentanyl and other synthetic opioids.

Recent high-profile deaths resulting following cocaine and fentanyl use include the football linebacker Jaylon Ferguson, the actor Michael K. Williams and the rapper Mac Miller.

Because fentanyl is a white powder that is cheaper and extremely potent, drug dealers use it as a bulking agent with cocaine, heroin and methamphetamine, as well as in counterfeit prescription pills like Xanax. That combination can prove deadly if drug users are unaware they are taking fentanyl and ingest too much.

Also, fentanyl has no smell or discernible taste, so the only practical way to check whether a drug has been laced is a test strip, which costs about $2 and takes about three minutes to show results. The leading manufacturer, BTNX, which is based in Markham, Ontario, claims an accuracy of 98 percent when used correctly.

The strips, however, are illegal in about half the states under old drug paraphernalia laws, according to the Kaiser Family Foundation. But with drug overdoses rising, lawmakers in several states are pushing to decriminalize the test strips. Alabama now allows fentanyl strips to be sold and the Pennsylvania House unanimously passed a bill to decriminalize the strips in June (it now awaits action in the Senate). Similar efforts are underway in Ohio, Iowa and Washington.

A new law in Illinois authorized pharmacists to distribute the strips, and in advance of Lollapalooza in late July, health officials in Chicago gave out strips and advised attendees to check their drugs for fentanyl.

Even in states with bans, test strips can be purchased online from stores like Bunk Police, a Nebraska company that sells test kits for recreational drugs, and nonprofit groups like DanceSafe, where a box of 10 fentanyl test strips sells for $19.99. Amazon sells them, too, with 10-packs of BTNX strips selling for $20.99.

DanceSafe strips came in handy last summer for the 43-year-old tech manager when she found a 2.5-ounce bag of cocaine outside a warehouse party in Williamsburg. She had naïvely assumed that such a large quantity would be clean but, to be sure, she took it home first to get it tested. The results came back positive.

“I threw away the whole thing, and everything that had even touched it, I was so freaked out,” she said. “That was a very good learning lesson for me.”