We report the identification of acetone (0.45 mg/mL) and isopropanol (0.17 mg/mL) but without the presence of ethanol in a blood sample from a man suspected of driving under the influence of alcohol. A preliminary breath screening test with an electrochemical instrument (Alcolmeter S-L2) was positive and an evidential breath-test with a dual wavelength infrared analyzer (Intoxilyzer 5000), recognized the presence of an interferant in the subject's breath. The man admitted drinking moderate amounts of alcohol (vodka) the previous evening and was being treated by his doctor for hyperglycemia by special dietary control. This case scenario provides a good example of severe metabolic ketoacidosis in an ostensibly healthy man driving on the highway. Biotransformation of the abnormally high concentration of blood-acetone to isopropanol occurs through the alcohol dehydrogenase pathway.