A breathalyzer reading above 0.08% can trigger a DUI arrest in Pennsylvania — but the machine is not infallible. Breathalyzers measure compounds in your breath that share a molecular structure with ethanol, which means certain medical conditions, foods, medications, and even environmental factors can cause the device to register a positive reading when no alcohol was actually consumed. If you received a high BAC result and believe it does not reflect your actual condition at the time of the stop, understanding the causes of a false positive breath test may be essential to your defense.
At Rubin, Glickman, Steinberg & Gifford, P.C., our DUI defense attorneys have represented clients across Montgomery County and Bucks County for over 65 years. We know how to scrutinize breathalyzer results, challenge testing procedures, and build a defense grounded in the facts of your specific case.
What Can Cause a False Positive on a Breathalyzer?
A breathalyzer does not directly measure alcohol in your bloodstream. It analyzes a sample of your breath and estimates your BAC based on detected compounds. Because of this indirect method, certain non-alcohol substances and conditions can trigger a positive result. The following are the six most commonly documented causes.
Diabetes and Ketosis
When the body cannot process glucose efficiently, it enters a metabolic state called ketosis, during which it burns fat for energy and produces acetone as a byproduct. Acetone is chemically similar to ethyl alcohol and can register on a breathalyzer as alcohol. Individuals with Type 1 diabetes in particular may experience elevated ketone levels that cause a breathalyzer to overestimate their BAC.
Acid Reflux and GERD
Gastroesophageal reflux disease (GERD) causes stomach contents, including any residual alcohol, to rise into the esophagus and mouth. This “mouth alcohol” can contaminate a breath sample and result in a reading significantly higher than the driver’s actual BAC. Officers are supposed to observe a 20-minute pre-test waiting period to account for this, but that protocol is not always followed.
Asthma Inhalers
Certain asthma inhalers contain compounds that can produce elevated readings on breathalyzer devices. This is a documented issue with older breathalyzer models in particular, though it can still occur with newer equipment depending on the specific inhaler formulation.
Mouthwash and Breath Sprays
Many over-the-counter mouthwashes and breath sprays contain significant concentrations of alcohol. If used shortly before a breath test, the residual alcohol in the mouth can skew the reading upward, particularly if the mandated waiting period was not observed.
Certain Foods and Beverages
Several foods have been shown to produce breathalyzer interference. These include ripe or fermented fruit, which produces trace amounts of ethanol as it breaks down, protein bars and energy drinks containing fermented ingredients, and pecans and certain breads made with yeast. These are not common defenses in isolation, but they can reinforce other challenges when combined with procedural errors in how the test was administered.
Environmental Contaminants
Paint fumes, industrial solvents, and other airborne chemicals contain compounds structurally similar to ethanol. Drivers who recently worked in environments where these substances were present — or who were exposed to them before being stopped — may register a falsely elevated reading. Breathalyzers used in traffic stops are not calibrated to distinguish between ethanol and these environmental compounds.
Procedural Errors That Support a False Positive Challenge
Beyond the physiological and environmental causes above, a breathalyzer result can also be challenged on procedural grounds. Common issues include the following:
- The device was not properly calibrated before the test
- The officer failed to observe the required 20-minute pre-test observation period
- Mouth alcohol from a medical condition or recent substance use contaminated the sample
- The officer was not certified to administer the test
Any of these errors can create grounds for challenging the admissibility or reliability of the result in court. According to PennDOT’s DUI legislation guidance, officers must follow specific protocols to ensure accurate breathalyzer results.
Frequently Asked Questions About False Positive Breath Tests
Can a breathalyzer give a false positive?
Yes. Breathalyzers estimate BAC by detecting compounds in breath that share a molecular structure with ethanol. Medical conditions like diabetes, acid reflux, and certain medications can cause the device to register a positive result even when the driver has not consumed alcohol. Procedural errors, equipment calibration failures, and environmental contaminants can also produce inaccurate results.
Does diabetes cause a false positive on a breathalyzer?
It can. Diabetic ketoacidosis causes the body to produce acetone, which breathalyzer devices can misread as ethyl alcohol. If you have diabetes and were charged with a DUI based on a breathalyzer result, your medical condition may be a relevant factor in your defense.
Can mouthwash cause you to fail a breathalyzer?
Yes, particularly if used shortly before testing. Mouthwash containing alcohol can linger in the mouth and produce a false reading, especially if the officer did not observe the required 20-minute waiting period before administering the test.
What happens if a breathalyzer test is inaccurate?
An inaccurate breathalyzer result does not automatically dismiss your DUI charge, but it can significantly affect your case. Your attorney can challenge the result by questioning calibration records, the officer’s certification, compliance with observation protocols, and any medical or environmental factors that may have interfered with the test.
Contact Rubin, Glickman, Steinberg & Gifford, P.C. About Your DUI Defense
A breathalyzer reading alone does not determine the outcome of a DUI case. If you believe your result does not accurately reflect your condition at the time of the stop, speaking with a skilled attorney as soon as possible gives you the best opportunity to preserve your defense options. At Rubin, Glickman, Steinberg & Gifford, P.C., our team has the knowledge and courtroom experience to challenge breathalyzer evidence effectively across Bucks County, Montgomery County, and surrounding southeastern Pennsylvania communities. We handle first-offense DUI cases through the most complex repeat-offense matters, and we are ready to fight for you.
To schedule a free consultation with our DUI defense team, complete our contact form today. The sooner you reach out, the more we can do to help.
Rubin, Glickman, Steinberg & Gifford P.C.
Pennsylvania Attorney's
August 20, 2026
