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How does a low carb diet cause a false-positive on an alcohol breathalizer test?

I know that a low carb diet causes energy to be created from fatty acids rather than glucose and that somewhere along the line ketones are created, which triggers the breathalizer. it is also the cause of severe diabetics to have the characteristic “sweet” breath.
But what are the cellular mechanisms for this? I can’t find any legit resources, but think this would be an interesting topic for an O-Chem presentation.



The ethyl alcohol molecule is composed of two carbon, one oxygen and six hydrogen atoms. Because of the mass of the atoms and the strength of the bond between the atoms, it absorbs light at a particular energy level. In the case of infrared alcohol breath testing instruments, light with a wavelength of about 3.39 is used because it is absorbed by the bond between the two carbon atoms. In reality, the
instruments are measuring the vibration of the methyl tail of the alcohol molecule.
A significant problem in measuring ethyl alcohol with infrared absorption is the presence of many substances on the human breath that have methyl tails such as acetone and methyl ethyl ketone. Acetone is present in the breath as a break-down product of fat metabolism in the body. Each of these molecules have methyl tails and absorb light in the methyl stretch region and thus can potentially cause a false positive or erroneously high breath alcohol reading.


I don’t think anything can fool the breathalizer test. They tried fooling one on Mythbusters and failed.


mate if this is true i,m off to the pub see ya


Ketones are produced when fatty acids are oxidized (burned for energy). You can find the specifics of fatty acid catabolism on any number of websites. This website is a start. The bottom two molecules, acetoacetate and acetyl-CoA are the ketones.
For an easier to swallow presentation, I would check your school’s library for a biochemistry textbook. Look for fatty acid metabolism. Specifically, the beta oxidation pathway for breaking down fatty acids.


I don’t know if the breathalyzer thing is true. Ketones are formed by the break down of fat for energy. Uncontrolled diabetes causes the body to only utilize fat for energy and causes a condition called “ketoacidosis”. The person afflicted with this condition can appear intoxicated, and their breath has a characteristic “fruity” smell.