Ketogenic (Keto) and low carbohydrate diets are among the more popular eating lifestyles these days. Someone on a strict Keto or other low carb diet metabolizes energy differently than a person who is eating a normal amount of carbs. The liver of a person on such diets breaks down fat for fuel, which creates acetone that may be released through the person’s breath. This is colloquially referred to a “being in ketosis.” The acetone can be reduced to isopropyl alcohol depending on the stage of ketosis

Anecdotal evidence (and a few scientific papers) supports a potential concern that someone on a Keto diet could cause a false positive on a breathalyzer. While the breath molecules expelled by a person in ketosis will not turn a 0.00% blood alcohol content (BAC)into a 0.08% BAC, a Keto diet may cause a breathalyzer to register over 0.08% for someone who, if not on a Keto diet, may have registered something below that. For example, someone who is in ketosis and has had a couple of drinks and might have a 0.06% true BAC, could potentially register 0.08% or more.

Law enforcement agencies use fuel cell breathalyzers, which supposedly can differentiate between ethanol molecules (those created by drinking alcohol) and other alcohol-based molecules, such as the Isopropyl molecules expelled when someone is in ketosis. However, I am unaware of any data that support this. While a blood test for BAC can establish that the driver’s BAC is under 0.08%, this can become more than an inconvenience for the driver. Beyond that, the driver who unwittingly chooses a breath test rather than a blood chemical test, may be stuck with a false positive result. A lesson here might be that if your

Another concern, now that installation of ignition interlock devices (IIDs)are now required following most DUIs, is whether a Keto diet may prevent these devices from operating. IIDs require a 0.00% BAC before a vehicle can be started. There is concern, although this has not been well-studied or documented, that IIDs are unable to distinguish the isopropanol molecules excreted from the breath of a person in ketosis from ethanol molecules. Even the slightest measurement of alcohol will be measured on an IID device.

It is not only those individuals on Keto diet who produce the ketones that, when processed by the liver, are expelled as isopropyl alcohol. People who have been fasting, who have diabetes or are in diabetic ketoacidosis, or are hypoglycemic may also produce ketones.

It is crucial that you tell your DUI defense attorney if you are on a Keto or low carb diet or if you have a medical condition that might interfere with the correct BAC measurement. The results of the breath tests can be challenged!

Orange County DUI attorney William Weinberg will challenge the results of your chemical testing whenever warranted. A successful challenge of the test results can result in a dismissal of the charges or may put doubt on their accuracy. If you have been arrested for driving under the influence, contactMr. Weinberg at his Irvine office for a free consultation regarding your options.  He may be reached by emailing bill@williamweinberg.comor by calling his Irvine office at 949-474-8008.

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