Some people are using fitness tracking devices such as Fitbit or Apple Watch to monitor their heart rate while they are using illicit drugs in an effort to prevent overdoses, CNBC reports.

Dozens of discussion threads have appeared on Reddit, Twitter and other social media about using tracking devices while taking cocaine, MDMA or other drugs.

Doctors say using a fitness tracker to monitor heart rate during drug use gives people a false sense of security. Ethan Weiss, a cardiologist at the University of California, San Francisco, said heart rhythm and blood pressure are also affected by cocaine use and aren’t trackable by most consumer smart devices. “Taking drugs is always a risk, whether you’re monitoring a tracker or not,” he said. “It’s possible this is leading people to do more cocaine.”