What Causes False Positive Breathalyzer Reading?

A man blowing into a breathalyzer.
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Every driver had at least one experience with a breathalyzer. This is a device that is used by police officers so they can check if there’s alcohol in the driver’s system. In most cases, the breathalyzer is used during sobriety tests. The device is inserted into the mouth of the person and then the display shows if there are amounts of alcohol.

The reading will determine if the BAC is under or above the legal limit.

However, in some cases, the BAC may show false results, especially if the person didn’t drink at all.

What to do in such cases? It’s best to consult a Portland DUI attorney even though if you were entirely sober.

What’s False Positive Reading?

When doing a breathalyzer test and it shows that you are over the legal limit, you likely have alcohol in your system. Today’s modern technology offers accurate devices and precise readings.

However, sometimes the breathalyzer test may show false reading.

Several factors can lead to this such as:

  • Contamination
  • Calibration of the equipment
  • Medical conditions
  • Time the test is given to drinking


Just like other technology, breathalyzers should be frequently calibrated to ensure proper work. If a test is done without proper calibration, the device can show a false positive breathalyzer. For the police officer to know they are getting the most accurate reading, the device should be set at specific settings.

Medical Conditions

Medical conditions and medications are other factors for false-positive reading. When you have a medical condition or taking certain medications it can cause acid in the stomach and esophagus could result in the breathalyzer showing that you have alcohol in your system. This happens because the condition or medication increases the BAC levels in the blood and may leave some presence of alcohol in your mouth.

Time of the Test

If you do the test at a certain point when the alcohol is absorbed in your blood, the breathalyzer may show false-positive results. This happens because the blood alcohol content might rise and then drop after you consumed it and you may be over the legal limit.


Sometimes the polluted air can affect the breathalyzer test. The device must be properly cleaned of chemicals in the air. If it is affected by contamination, there’s a chance that the breathalyzer will show a false-positive result.

What Can Set Off a Breathalyzer

These devices were designed to detect the blood alcohol content of a person. Now more than ever, breathalyzers show accurate readings, however certain factors like medications and acetone can set the device off.

As stated before, taking medications can create an excess of acid in your body which can lead to a false positive reading.

Medications that create an excess of acid in the body can lead to a false positive breathalyzer result.

Acetone, on the other hand, is in the breath of every person and at times the levels may increase. When that happens, the breathalyzer will show false positive reading.

Hypoglycemia is a condition that will cause the presence of acetone in the breath, so it can make symptoms of intoxication. If you’re following a low-carb diet, it will increase the acetone levels which in the time of taking the breathalyzer test will show the presence of alcohol even if you didn’t drink at all.

What Happens if You Fail a Breathalyzer Test?

Failing the breathalyzer test will lead the officer to assume that you have a high level of alcohol in your body. They will arrest you and charge you with DUI. If you believe that the breathalyzer test showed a false reading (especially if you didn’t drink and have a certain medical condition or take medications) you’ll have to prove that in court.

This isn’t a simple thing and it’s best if you do it with the help of a skilled DUI attorney.

Some people wonder if they can deny a breathalyzer test. You have the right to do that, but it’s not a smart decision. Even if you haven’t been drinking, the officer may suspect that you did because you were speeding or was responsible for another traffic violation.

Take the test and if it’s necessary, you’ll do your best later to prove that the breathalyzer showed a false positive reading.

Our team at Trilogy Law Group has a history with such cases. Let us review your case and help you prove your innocence. Contact our office today and schedule your first free case review.

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