WTF?! Wearables such as the Apple Watch and Fitbit’s activity trackers are great for monitoring users’ heartbeats, letting them tailor their exercises to create efficient routines. But, like so many devices, people are finding alternative uses, one of which is keeping track of heart rates during cocaine binges.

Speaking to CNBC, tech worker Owen (not his real name) talked about a time two years ago when his Fitbit showed a heart rate of 150 bpm even though he’d been sitting down for hours. The reason? He’d been snorting lines of cocaine at a bachelor party.

"My heart rate only gets to 150 if I'm running, like really intense physical activity," he said. "If I'm in a really stressful work meeting, I might get close to 100 or 120."

To make sure the elevated heart rate was caused by the drug, Owen handed his Fitbit to a new arrival at the party. 20 minutes after his friend had done a line, their heartbeat also jumped from 80 to 150.

The dopamine and adrenaline hit cocaine provides is what causes people’s heart rate to spike so rapidly. Many of the 5000+ deaths it causes each year are due to heart attacks, strokes, and angina. And while users like Owen believe wearing a Fitbit will keep them safe while binging, medical experts say they don’t help and can give people a false sense of security.

"If someone says, 'Let's do a line,' I'll look at my watch," Owen said. "If I see I'm at 150 or 160, I'll say, 'I'm good.' That's totally fine. Nobody gives you a hard time."

Many users on Reddit and various social media sites are lauding their Fitbits and Apple Watches as essential tools when taking drugs. "Drugs are basically the only reason I wear a Fitbit," said one Redditor. "I want an early warning system for when my heart's going to explode."

DrugsLab, a YouTube channel with half a million subscribers, shows the effects drugs have on heart rates and body temperatures. The hosts take substances while their body stats appear on a board behind them. They say the channel helps educate millennials about drugs.

Unsurprisingly, those in the medical profession don’t recommend relying on Fitbits and Apple Watches to keep you safe while snorting down mountains of coke. Not only can these devices be inaccurate, but cocaine can also affect heart rhythm and blood pressure—two things most trackers don’t monitor.