Can Coffee Make You Fail a Breathalyzer? The Surprising Truth Revealed

I love a good cup of coffee in the morning, don’t you? There’s something so comforting about the aroma and taste of freshly brewed coffee. But have you ever wondered if drinking that cup of joe could affect your ability to pass a breathalyzer test? Well, you’re not alone. Many people have questioned whether coffee can have any impact on the accuracy of a breathalyzer reading. So, let’s dive in and uncover the surprising truth behind this popular question.

The Basics of Breathalyzer Tests

Before we explore the potential connection between coffee and breathalyzer results, we need to understand how these tests work. A breathalyzer measures the concentration of alcohol in a person’s breath to determine their blood alcohol content (BAC). It does so by analyzing the ethanol molecules present in the breath sample.

How Does Alcohol Enter Your Breath?

When we consume alcohol, it is absorbed into our bloodstream through the stomach and small intestine. From there, it gets metabolized in the liver. During this process, a certain percentage of alcohol is converted into acetic acid and released as carbon dioxide through our lungs when we exhale. It’s this exhaled breath that a breathalyzer detects to estimate a person’s BAC.

Does Coffee Alter Breathalyzer Results?

Now that we have a basic understanding of breathalyzers, let’s address the question at hand – can coffee make you fail a breathalyzer? The answer is… not really.

The Role of Coffee in Breathalyzer Results

Coffee itself does not contain alcohol, so it won’t directly impact your breathalyzer reading. The presence of coffee in your system won’t falsely raise your BAC. However, there are some factors related to coffee consumption that might indirectly affect the test results.

Factors That Can Influence Breathalyzer Accuracy

1. Mouth Alcohol: One possible scenario is if you drank an alcoholic beverage shortly before your cup of coffee. In this case, the alcohol might still be in your mouth, unfairly raising the breathalyzer reading. However, this issue has nothing to do with coffee itself but rather the residual alcohol in your oral cavity.

2. Breath Fresheners: Some coffee lovers may add breath freshening products to their java, such as peppermint or mint gum. These products can potentially contain alcohol, which, if present in your mouth, could raise the BAC reading.

3. Coffee Liqueurs: While coffee alone won’t affect the results, certain alcoholic coffee beverages like Irish coffee or coffee liqueurs do contain alcohol. So, if you’ve enjoyed one of these drinks, it’s the alcohol content, not the coffee, that can influence your breathalyzer reading.

4. Dehydration: Excessive coffee consumption can lead to dehydration. When dehydrated, your body eliminates alcohol less effectively, increasing the concentration in your breath. This dehydration effect is not unique to coffee. Other factors like alcohol consumption, medication, or other diuretics can also contribute to dehydration and impact breathalyzer results.

The Reliability of Breathalyzer Tests

While coffee might not directly impact breathalyzer results, it’s important to understand that these tests are not flawless. They have their limitations and can yield inaccurate readings for various reasons.

External Factors Affecting Breathalyzer Accuracy

1. Calibration: Breathalyzer devices need to be regularly calibrated to ensure accurate readings. If a device is improperly calibrated, it can result in false readings.

2. Environmental Contaminants: Some substances found in the environment can interfere with breathalyzer results. For example, certain cleaning agents, paint fumes, or other volatile chemicals may produce false positives.

3. Medical Conditions: Certain medical conditions, such as GERD (gastroesophageal reflux disease) or diabetes, can potentially affect breathalyzer results.

4. Timing of Testing: Breathalyzer tests should ideally be conducted within a specific time frame after alcohol consumption for optimal accuracy. Taking the test too soon or too late can skew the results.

Professional Accuracy versus Personal Breathalyzers

It’s worth mentioning that the breathalyzer tests performed by law enforcement agencies are generally more accurate compared to personal portable breathalyzers. Those portable devices may not be as reliable due to various factors like sensor quality, calibration, or interpretation errors.


So, can drinking coffee make you fail a breathalyzer test? The simple answer is no. Coffee alone won’t lead to a false positive. However, certain factors related to coffee consumption, like mouth alcohol or the addition of alcoholic substances, can indirectly impact breathalyzer readings. It’s essential to understand the limitations and potential external factors that can affect the reliability of breathalyzer tests. If you find yourself in a situation where your BAC reading is unexpectedly high, you may consider seeking legal advice to explore alternative explanations and defense strategies. But for now, go ahead and enjoy your morning cup of coffee without worrying about its potential impact on your breathalyzer results.

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