Can a Keto Diet affect a Breathalyzer Test?

The Keto Diet has become pretty popular in the past few years as a way to lose weight and manage both types of diabetes. It’s a diet that goes low on carbs and high on healthy fats to deprive the body of easy access to glucose, forcing it to turn fat stores into energy molecules known as ketones and burn these for energy instead.

We’re not here to go in-depth on the science of the Keto Diet or whether or not you should go on one, though. If you happen to be already involved in some keto diet circles, chances are you’ve heard seemingly apocryphal stories about people on a ketogenic diet failing breathalyzer tests without ever consuming alcohol.

This is especially frustrating because as anyone earnestly attempting a ketogenic diet knows, consuming alcohol is the last thing you want to do. This is because alcohol is basically pure sugar – carbohydrates! – and the very thing that a ketogenic diet is supposed to cut out.

Unfortunately, though, not all the tales of failing a blow test on a keto diet are urban legends. It happened to a flight attendant in 2020 and the phenomenon was acknowledged in a research paper published in the International Journal of Obesity back in 2007.

According to that paper, a 59-year-old Swedish man failed an ignition interlock test on a company car, which shouldn’t have happened because he was a lifelong teetotaler. Curious as to what was going on, he contacted researchers at the Karolinska University Hospital in Stockholm, Sweden for help.

While researchers weren’t able to study the man directly, they did determine that the most plausible explanation was that his breath triggered the device because of the presence of ketones like beta-hydroxybutyrate and acetone in his breath.

Experienced keto dieters will know that this diet comes with an interesting side effect. Called “keto breath,” it’s a phenomenon where one’s breath is said to smell like nail polish remover. That’s because ketones like acetone are present in every exhalation. This isn’t so much the problem as the fact that the body sometimes breaks acetone down into isopropanol alcohol, which registers the same as the ethanol alcohol that a breathalyzer is meant to detect.

The good news here is that the problem lays in your breath. If you submit to a blood test, it could reveal that the only alcohol in your body is the acetone your body made in ketosis. In the best possible scenario, though, you won’t have to get that far.

It’s critical to inform anyone performing a breathalyzer test that you are on a keto diet. With this variable recorded, it can help add clarity to the situation should you test positive for alcohol in your system.

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