Can Diet Pills Cause a Breathalyzer False-Positive?

Posted by Jon Ibanez on September 8th, 2014

Just because the summer is coming to an end doesn’t mean people aren’t dieting. And when the weather doesn’t permit running on the beach, dieters often turn to dieting pills. If a person happens to find themselves in the unfortunate position of blowing into a breathalyzer because law enforcement suspects them of driving drunk, can the diet pill affect the breathalyzer accuracy? Ask model and actress, Hayley Hasseloff.

The daughter of David Hasselhoff recently filed a writ of mandate to set aside a California DMV order suspending her license. The license suspension stemmed from a 2012 DUI arrest in Los Angeles.

Hasselhoff claimed that she only had one alcoholic drink more than two hour prior to taking a breathalyzer test. However, because she had taken the diet pill, Phentermine, the breathalyzer produced a false-positive.

Diet pills cause the body to burn stored fat. This process produces ketones. Ketones are water-soluble products of fat metabolism. Our bodies use ketones for energy. Whatever ketones the body doesn’t use, it releases in urine and through the lungs. Ketones which are released through the lungs can be detected in the breath.

When the ketones are released through the lungs, their chemical composition is similar isopropanol which is a type of alcohol.

This process, can occur when a person goes on a low carbohydrate diet and the body turns to ketones for energy rather than glucose produced by the carbohydrates.

Unfortunately, a breathalyzer cannot differentiate between isopropanol and ethyl alcohol, the alcohol found in beer, wine, and cocktails.

What’s more, when a person’s body is going through the early stages of the ketosis process, they may experience tiredness or fatigue, weakness, dizziness, nausea, and frequent urination. Sounds a lot like the symptoms of intoxication, doesn’t it?

I’m not a doctor and this is, of course, a very simplified version of the process. But to affirm the testimony of the expert that Hasselhoff introduced to explain this process, the answer is yes, a diet pill can cause a false-positive on a breathalyzer.

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