False Positives on Ignition Interlock After Low-Carb Diet

Posted On October 09, 2023 Charles Ramsay

Imagine: To start your car, you must blow into a breathalyzer. You made a mistake years ago, and now you have to pay a hefty monthly fee to have a breathalyzer, known as an ignition interlock device, installed in your car to drive to work.

Aside from the money, hassle, and embarrassment, it's been fine. But now, it's giving false positives. How could it be? You haven't had anything to drink.


The problem with ignition interlock devices is that they aren't specific to ethanol — the type of alcohol that is beer, wine, and liquor. They operate on fuel cell technology.

Fuel cells take any alcohol and convert it into electrical energy, releasing electrons in the process. The more electrons released, the higher the alcohol reading it gives.

But here's the problem: You just went on a ketogenic diet (low-carb), and now it's reading the isopropyl alcohol on your breath as a positive reading. As you burn fat, one of the byproducts is acetone. Acetone then gets converted into isopropyl alcohol.

There’s even a scientific case study about this problem in the scientific literature.

In Sweden, every government car comes with an ignition interlock installed. A man who was a complete teetotaler started getting false positives. This was preventing him from doing his job.

When scientists investigated, they found that the man had just gone on a ketogenic diet (low-carb) and found that his diet was to blame for the false positives.


If you’ve had a false positive on your ignition interlock, the state won’t look into the science for you. They’ll see the positive numbers and try to tack on more time you must pay to keep your ignition interlock on your car.

At Ramsay Law, we look into the science behind each cast to ensure you’re getting the best deal possible.

We know the science inside and out and look at every aspect of your case to get the best possible outcome.

Call us to discuss your case. Contact Ramsay Law at 651-604-0000.

P.S. - Stay up to date by subscribing to our blog, where we explore the intersection of law and science around DWI cases.

Daniel Koewler