When an individual who has not consumed alcohol registers a positive result on an alcohol test, it is often alarming. This phenomenon occurs most frequently in people with diabetes. Metabolic changes within the body produce compounds that testing equipment mistakes for ethanol, the alcohol found in drinks. Understanding this issue requires looking into the body’s internal fuel processing and how standard testing devices function. The underlying biological mechanism explains why a person can be completely sober yet fail an alcohol screening.
Diabetic Ketoacidosis and the Production of Acetone
The primary metabolic cause for a false-positive alcohol reading in a diabetic patient is Diabetic Ketoacidosis (DKA). DKA develops when the body has a severe deficiency of insulin, the hormone that allows cells to use glucose for energy. Without sufficient insulin, glucose builds up in the bloodstream, and the body’s cells signal for an alternative fuel source.
In response to this energy crisis, the liver rapidly breaks down fat stores (lipolysis), releasing free fatty acids. These fatty acids travel to the liver, where they produce acetyl-CoA. Because the body cannot efficiently process acetyl-CoA for energy due to the lack of insulin, it is shunted into ketogenesis, resulting in the creation of ketone bodies.
The three main ketone bodies produced are acetoacetate, beta-hydroxybutyrate, and acetone. Acetone is unique because it is a volatile compound that easily evaporates into a gas. As acetone accumulates in the blood during DKA, the body attempts to excrete the excess through the lungs. This excretion gives the breath of a person in DKA a distinct, “fruity” odor. The high concentration of volatile acetone in the breath interferes with alcohol testing devices.
Mechanisms of Cross-Reactivity in Alcohol Testing
The reason acetone is mistaken for ethanol lies in the design of common alcohol testing instruments, particularly breathalyzers. Breathalyzers measure the concentration of ethanol in the breath to estimate blood alcohol concentration. However, many devices are susceptible to “cross-reactivity” with other volatile organic compounds.
One common device, the electrochemical fuel cell breathalyzer, uses a chemical reaction to oxidize ethanol and produce an electrical current. The strength of this current registers as the alcohol reading. Acetone, which is also a volatile organic compound, can undergo a similar oxidation reaction within the fuel cell. This generates a current that the device interprets as ethanol.
Another technology, infrared spectroscopy, measures alcohol by detecting how molecules absorb light at specific wavelengths. Ethanol absorbs infrared light most strongly at a particular wavelength. Acetone also absorbs light at similar, though slightly different, wavelengths. Older instruments may not perfectly distinguish between the absorption patterns of ethanol and high concentrations of acetone, leading to a false-positive reading. Modern evidential breath testers mitigate this issue by using multiple wavelengths to differentiate between ethanol and interferents like acetone. Blood tests, particularly those using gas chromatography, are much more accurate because they chemically separate and identify each specific compound.
Endogenous Ethanol Production and Isopropanol Formation
While DKA is the most common cause of false-positive readings, two other biological processes can contribute to alcohol-like substances in the body. One rare condition is Auto-Brewery Syndrome (ABS), where an overgrowth of yeast in the gastrointestinal tract ferments ingested carbohydrates. This fermentation produces measurable amounts of ethanol internally.
The ethanol produced in ABS is chemically identical to beverage alcohol, meaning it registers as a true positive on any alcohol test. This internal brewing process can cause intoxication symptoms and positive test results even without consumption. A secondary cause involves the metabolic fate of high levels of acetone produced during DKA.
The body can convert acetone into isopropanol (isopropyl alcohol) through a reduction reaction. Isopropanol is the intoxicating agent found in rubbing alcohol and registers on some alcohol tests. This conversion is more likely when acetone levels are extremely high, such as during severe ketoacidosis. Therefore, a person may have elevated levels of both cross-reactive acetone and intoxicating isopropanol without consuming external alcohol.
Clinical Differentiation and Management
Medical professionals must quickly differentiate between true alcohol intoxication and a metabolic event like DKA, as treatments are vastly different. Diagnosis involves a detailed laboratory workup, focusing on blood glucose levels and specific metabolic markers. A patient with DKA typically shows severe hyperglycemia, often exceeding 250 mg/dL, alongside a high anion gap and ketones in the blood and urine.
The primary management for DKA involves intravenous fluids and insulin therapy to halt ketone production and correct the metabolic imbalance. Conversely, intoxication with ethanol or isopropanol requires supportive care until the body metabolizes the substance. If an alcohol test is administered by law enforcement, the individual should immediately state their diabetic status and request a blood test, which accurately measures specific compounds.
The legal implications of a false positive are significant. While modern law enforcement devices are increasingly designed to identify acetone interference, a positive reading can still lead to detention. Carrying medical documentation, such as a doctor’s note or a medical alert card, is important in such encounters. The most effective management is treating the underlying DKA, which eliminates the source of the interfering acetone, resolving both the metabolic emergency and the testing issue.