Ketones and False-Positive Breath Alcohol Tests
Yes, there is medical literature supporting that endogenous ketone bodies can cause false-positive elevated breath alcohol readings, specifically through the metabolic conversion of acetone to isopropanol.
Mechanism of False-Positive Results
The biochemical pathway is well-established: during ketosis (from fasting, ketogenic diets, or diabetic ketoacidosis), acetone—one of the three primary ketone bodies—is produced through spontaneous decarboxylation of acetoacetate 1. Acetone can be reduced in the body to isopropanol by hepatic alcohol dehydrogenase (ADH), and breath alcohol testing devices respond to isopropanol, leading to false-positive results 2.
Key Evidence
A 2007 case report documented a teetotaller on a very low calorie diet (VLCD) who failed an alcohol ignition interlock device due to ketonemia with high concentrations of acetone, acetoacetate, and beta-hydroxybutyrate 2. The electrochemical oxidation method used by the interlock device detected isopropanol (the metabolic product of acetone), not ethanol.
A 2019 military case identified an asymptomatic sailor with developing diabetic ketoacidosis through an elevated breathalyzer reading during routine duty reporting 3. The acetone generated in DKA was converted to isopropanol, which was detectable by the breathalyzer despite no alcohol consumption.
A 1994 forensic case demonstrated that breath alcohol instruments can detect isopropanol and acetone as interferants, with blood analysis confirming the presence of isopropanol (0.023 g/100 mL) and acetone (0.057 g/100 mL) alongside ethanol 4.
Important Caveats and Clinical Context
When False-Positives Occur
False-positive results are most likely in states of significant ketosis:
- Diabetic ketoacidosis (DKA) - where total serum ketones exceed 0.5 mmol/L and can reach much higher levels 1
- Ketogenic diets or very low calorie diets - inducing nutritional ketosis 2
- Prolonged fasting - shifting metabolism toward ketone body production 1
- Alcoholic ketoacidosis - where the redox state favors beta-hydroxybutyrate formation 1
Contradictory Evidence
A 1989 study found no cross-reaction between ketone bodies and breath alcohol tests in nine grossly ketotic diabetic subjects using Alcotest and fuel cell electrode methods 5. However, this study did not account for the metabolic conversion of acetone to isopropanol, which is the actual mechanism causing false-positives rather than direct cross-reactivity.
Clinical Implications
Safety-Sensitive Occupations
This phenomenon has significant implications for individuals in safety-sensitive work (bus drivers, airline pilots, commercial vehicle operators) who undergo random breath-alcohol testing 2. A person in ketosis from legitimate medical or dietary reasons could face employment consequences from false-positive results.
Diagnostic Approach
When encountering an unexpected positive breath alcohol test:
Assess for ketosis symptoms: fruity breath odor, recent fasting, ketogenic diet adherence, diabetes history, or symptoms of DKA (nausea, vomiting, abdominal pain) 3
Obtain confirmatory blood testing: Gas chromatography can distinguish ethanol from isopropanol and acetone 4
Check blood glucose and ketone levels: Blood beta-hydroxybutyrate measurement is preferred over urine ketone testing 1
Consider the testing device: Modern infrared instruments have methods to distinguish ethanol from acetone, but procedural or instrumental problems can still produce false-positives 4
Key Pitfall
Do not assume a positive breath alcohol test definitively indicates ethanol consumption without considering metabolic causes, particularly in individuals with diabetes, those following ketogenic diets, or anyone presenting with signs of metabolic derangement 2, 3.