The keto diet sends your body into a state of ketosis, which is when you are no longer burning carbohydrates for fuel but are instead burning up the fat stores in your body. Like most of what happens in your body, this chemical process results in the release of byproducts. In the case of ketosis, the byproduct is acetone, which metabolizes to isopropyl alcohol on your breath, and this could be trouble if police pull you over under suspicion of DUI.
How does it work?
When police stop a suspected drunk driver, they have many ways of determining if the driver is impaired. An officer may have smelled your breath, listened for you to slur your words or made you walk a straight line. However, the key to your arrest is often the portable breath test that measures the molecules you exhale.
Breath that contains alcohol has more molecules than regular breath, but not all portable breath machines can tell the difference between ethanol alcohol from an adult beverage and isopropyl alcohol as a byproduct of ketosis. The machines that can differentiate may not discern when you are in ketosis and have consumed alcohol, and this combination may be enough to unfairly push your blood alcohol concentration over the legal limit.
What are my options?
While achieving a .08 BAC simply by being on the keto diet, even if you have a drink or two, is not likely to happen, ketosis may raise your BAC just enough to violate your ignition interlock. If you have an interlock device on your vehicle because of a previous DUI or because your company equips its vehicles with IILs, acetone on your breath may give a false reading just high enough to lock you out.
However, the keto diet is not the only thing that can cause your body to emit acetone or isopropyl alcohol. Diabetes, acid reflux and certain medicines may affect the reading of a portable breath test. Whether you have any of these risk factors or not, your safest course of action is to refuse to take the roadside breath test and submit only to the more advanced machines at the police station. You may also wish to obtain legal advice to discuss your options.