False positives occur on DWI breathalyzer tests more often than you might think. Breathalyzer testing equipment always comes with its margin of error, and the test is administered by a person who is not infallible. A lesser-known potential cause of a false positive on a DWI test is the diet of the person being tested. For example, a keto diet, low carb diet, or intermittent fasting may cause false positives on DWI breathalyzer tests.
The Problem with Ketosis Breath
When we eat keto-based foods, such as nuts, berries, lean meat, fatty fish, and fresh greens, our bodies break them down into ketones, which have a chemical compound similar to isopropyl alcohol. This process is called ketosis, and the rate at which it occurs varies by person.
Those on a keto diet eat primarily or exclusively keto-based foods, and ketosis creates an elevated level of ketones in their bodies, which may register as a false positive on a breathalyzer test because some tests do not distinguish between different types of alcohol; for intoxication, the level of ethyl alcohol (ethanol) is the one that matters.
Note that ketones may also be prevalent in the bodies of those who have anorexia, bulimia, or diabetes or who are on other high protein/low carb diets such as Paleo, South Beach, or Atkins. Just as with the keto diet, the individual does not have sufficient carbohydrates or insulin to produce energy and regulate blood sugar, leading to the production of ketones.
To avoid this false positive from ketosis, you can actively try to get your body out of the ketosis process before driving. You can counteract ketosis by eating a banana or drinking fruit juice, which can also help reduce the kinds of signs and symptoms that suggest intoxication, such as decreased coordination, a flushed face, and sometimes even the smell of alcohol on the breath, often called “ketosis breath.”