Low-carb diets -such as the Atkins diet or the Ketogenic diet- have been around for decades. Nonetheless, this type of diet can cause problems for California drivers. It may cause a breath test provided by a California driver who was pulled over or arrested on suspicion of a DUI to falsely show the presence of alcohol – even if the driver had not consumed any alcohol that day.

Here’s how: A low-carb diet deprives the body of glucose, an important source of fuel for the body. In the absence of this source of fuel, the body turns to its fat for fuel. The process of turning fat into fuel produces ketones. When the body produces ketones and uses them for fuel, the body is in a state of ketosis. When the body is in a state of ketosis, ketones can be detected in that person’s breath. (This explains the bad breath that some report while on a low-carb diet). These ketones have a chemical composition similar to isopropyl alcohol. Many breathalyzer testing devices cannot distinguish between isopropyl alcohol molecules and ethyl alcohol molecules.  As such, a breath testing machine used in a DUI investigation may falsely detect the presence of alcohol simply because the suspect is on a low-carb diet.

It is doubtful that the amount of ketones in anyone’s breath could be sufficient to result in a breath test result showing a blood alcohol concentration at or greater than the .08% legal limit without the person having had consumed some alcohol. However, a person who would have otherwise been below the .08% legal limit may end up with a breath test result at or greater than the legal limit if that person is in ketosis. For example, someone who is in ketosis and has a true blood alcohol concentration of .06% could potentially register at 0.08% or more.

California Vehicle Code 23612(a)(2)(A) allows drivers arrested for suspicion of a DUI to choose between submitting to a breath test or a blood test. Unless the chosen test is not available, the officer must perform the test selected by the driver. Drivers on a low-carb diet may want to avoid submitting to the breath test to avoid being stuck with a false positive result.

Any driver arrested for a DUI should immediately hire an attorney. If you are on a low-carb diet, it is crucial that you tell your attorney.

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