Does the Keto Diet Affect Breathalyzer Tests?

In recent years, the ketogenic – “keto” – diet has become a popular way for people to manage diabetes and lose weight. The diet emphasizes limiting carbohydrate intake (less than 50 grams) and eating more protein and healthy fats. This deprives the body of glucose, the excess of which gets stored as body fat. When the body runs out of glucose to burn, it uses to the body’s fat stores for energy in a process known as ketosis.

By now, you’re probably wondering what any of this has to do with getting pulled over for DWI or blowing over the limit on a breathalyzer test. Bear with us, because explaining the basic science of how the ketogenic diet works is essential to explaining how it could land you in jail.

If you’ve ever looked into the ketogenic diet, you know how crucial it is to keep your body in ketosis. You also know how easily it can get knocked out of ketosis when you eat or drink too many carbs. While there are a few pure alcohols that don’t have carbs, many on the keto diet choose to stay sober so they don’t interrupt ketosis by having one drink too many.

This is why it’s especially unfortunate when someone on the keto diet blows a blood alcohol concentration (BAC) of 0.08% or higher on a breathalyzer test – they could have been completely sober at the time they were pulled over. So it begs the question: Why and how is this possible?

Ketones, Acetone & ‘Keto Breath’

When the body is in ketosis and uses fat stores for energy, it converts fat into energy molecules called “ketones.” When enough ketones are present in the body, they can end up getting exhaled each time the dieter takes a breath. If you haven’t heard of “keto breath” before, it’s a normal condition that occurs in ketosis when someone’s breath can smell like nail polish remover due to the presence of ketones – particularly acetone – in their breath.

This, however, was a problem for a 59-year-old Swedish man who failed to the ignition interlock system on his company car. He was a lifelong teetotaler on the keto diet, so he reached out to researchers with the medical curiosity for an explanation.

Although researchers didn’t study the man directly, they determined in a 2007 research paper that the presence of ketone molecules like beta-hydroxybutyrate and acetone created by ketosis could have triggered the ignition interlock system.

This implies that false positives can occur on other devices that detect alcohol in someone’s breath. Most simple breathalyzers, for example, can’t detect the difference between acetone created during ketosis from ethanol, which is found in beer and wine. There are those that can, but for the most part, all a breathalyzer detects is alcohol, so any and every type of alcohol molecule counts toward the BAC it registers.

In 2020, a flight attendant found this out the hard way when he failed a breathalyzer test at work despite claiming he hadn’t been drinking but was on the keto diet. There doesn’t appear to be much information as to what happened in this case, but it’s worth noting that blowing an illegal BAC during a DWI stop because of the keto diet is more than an urban legend.

So, Should Is Staying on the Keto Diet Risky?

In reality, a lot of unfortunate things have to line up for you to get charged with a DWI because of the ketones in your breath.

A police officer would have to pull you over, suspect you of DWI while you’re completely sober, actually make you blow a breathalyzer, have a less sophisticated breathalyzer that can’t detect the difference between ketones and ethanol, and follow through with the arrest.

If you are arrested for DWI under any circumstance, the best thing to do is to contact a DWI attorney like someone from our office for help. Rodriguez & Gimbert, P.L.L.C. represents clients who are accused of driving while intoxicated and can help them fight their charges.

For more information or to request a consultation, please contact us online.