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Factors that can negatively influence BAC tests during a DUI stop

The Pennsylvania Department of Transportation reported that police in the state made over 42,000 DUI arrests in 2022. Driving under the influence remains one of the chief concerns for traffic safety officials. When an officer stops a vehicle under suspicion of DUI, they often employ a breath test to gauge the driver’s blood alcohol concentration.

However, while these tests aim to offer a rapid and precise assessment of intoxication, certain factors can negatively influence the results. Understanding these variables can make you more aware of the complexities surrounding BAC tests and their potential inaccuracies.

Medications and mouthwash

Over-the-counter and prescription medications might affect the BAC reading. Some medicines contain alcohol, which can linger in the mouth and distort the test outcome. Similarly, many mouthwashes and breath fresheners also have a high alcohol content. Using them shortly before taking a breath test can produce a falsely elevated reading.

Medical conditions

Several medical conditions can influence BAC test results. For instance, individuals with acid reflux, heartburn or gastroesophageal reflux disease might regurgitate stomach alcohol into the mouth. This can lead to higher than accurate readings on a breath test. Additionally, conditions like diabetes can produce acetone in the breath, which some breath tests might mistakenly identify as alcohol.


Believe it or not, your diet can also affect BAC readings. Diets high in protein and low in carbohydrates, such as the keto diet, can produce elevated levels of acetone in the breath. As mentioned before, certain devices can misinterpret acetone as alcohol, leading to inaccuracies.

Breathing patterns

How you breathe can impact the results of a breath test. Hyperventilating might reduce the concentration of alcohol in your breath, potentially leading to a lower reading. On the other hand, holding your breath or taking a deep breath before blowing into the device can increase the alcohol concentration, yielding a higher reading.

External environmental factors

Factors like paint fumes, cleaning chemicals or gasoline vapors can interfere with the test if inhaled prior to blowing into the breath tester. These substances can linger in your mouth or respiratory system and might be mistaken for alcohol by the breath tester.

While BAC tests serve as valuable tools in assessing a driver’s sobriety, they come with their set of limitations.  Being aware of these influences can help you make informed decisions and understand the intricacies of BAC readings during a DUI stop. Always prioritize safety and avoid driving if you have consumed alcohol or are under the influence of any substance that impairs your abilities.