Imagine you hear that everyone at work must take a breathalyzer test. No biggie—you haven’t been drinking. You stride into the office, blow into the tube, and stare in disbelief at the results: 0.05% BAC. That’s it—enough to get fired. How could this be? One doctor warns the popular “Keto” weight-loss diet can fool a breathalyzer.

American Airlines flight attendant fired over BAC, claims it was Keto

Andre Riley had been a flight attendant with American Airlines for eight years when he failed a breathalyzer test. He blew a 0.05% BAC. And that was it—his second strike—and he was fired.

Riley insisted, “I wasn’t drinking. I wasn’t doing anything, just because I changed my diet.”

He explained he suffers from “Jared Disease Autobureau Syndrome.” The ketosis diet (also called the Keto diet) is an extremely low-carb diet originally developed to prevent epileptic seizures a century ago. It’s now prescribed by doctors for various conditions and has become trendy for weight loss and performance, popularized by celebrities like Halle Berry, Kourtney Kardashian, and LeBron James. But doctors warn of an unintended consequence.

The Keto diet may lead to breathalyzer DUI false positives

Dr. Ryan Lowery, an author at Ketogenic.com, broke down the DUI false positives: “You create something known as acetone. With acetone some of that gets released as something known as isopropyl alcohol.”

No, isopropyl alcohol is not the same “active ingredient” in your Taco Tuesday margarita; and no, Keto diet practitioners aren’t buzzed all the time. But it doesn’t matter. “Some breath analyzers that detect for DUIs and things like that aren’t able to differentiate between ethanol alcohol and isopropyl alcohol.”

Can you fight a breathalyzer DUI false positive?

If a roadside breathalyzer test shows your BAC above 0.08%, the investigating police officer has all the evidence needed to arrest you for driving under the influence—even if you’re on the Keto diet.

But in 46 states, that roadside test is voluntary. Police can still arrest you if they have other evidence—such as slurred speech or swerving. If they do, they’ll take you to the station, where a much more accurate breathalyzer is available.

Andre Riley has fewer rights when dealing with an employer. But he still plans to fight his test results and try to get his old job back. “I don’t want to be punished and take consequences for something that I didn’t do.”