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Possible causes of breath test false positives

On Behalf of | Sep 23, 2021 | DWI

In many cases, a positive result on a breath test is enough to land you behind bars. Since this is a key piece of evidence, you would expect that it is unfailingly accurate. Unfortunately, this is not always the case.

According to WebMD, a problem with the test itself could affect its accuracy. For example, it could need a software update or a battery replacement and yield an incorrect reading as a result. However, sometimes a false positive happens because of a perfectly normal, legal thing that you did before getting behind the wheel. If you received a positive breath test that you do not think was accurate, maybe one of the following was to blame.

Keto diet

If you are health conscious, you may have adopted the ketogenic diet. The keto diet involves eating lots of protein to force your body into ketosis so it breaks down fat for fuel. According to Men’s Health, isopropyl alcohol is a byproduct of the process and could cause a positive result on a breath test.


Mouthwash and other breath fresheners sometimes contain trace amounts of alcohol. This is to act as an antiseptic to kill germs that cause bad breath. The percentage of alcohol in these products is very small, so much so that the government does not regulate them. However, if you used one of them shortly before driving, a breath test could pick up on the alcohol and yield a false result.

When it comes to personal hygiene products containing alcohol, which also includes hand sanitizer, the chances of a false positive increase depending on how recently before the test you used it. To reduce the risk, you should avoid these products for at least 15 minutes prior to getting in the car.