Can diabetes or a keto diet cause a false positive breath test?

Both diabetic ketoacidosis and sustained ketogenic dieting produce acetone and related compounds in the body, and there's a long-running argument about whether infrared breath instruments can misread them.

The realistic assessment: this isn't a defense that stands on its own. Modern evidentiary instruments include features intended to detect interfering substances, and asserting a keto diet without more won't move a case.

Where it becomes relevant is in combination. A documented diabetic condition, a reading that doesn't match the observed behavior, an unusual instrument response, or a gap between the two samples — those together are worth developing, and generally with expert input rather than argument alone.

The approach is the same as with reflux. Compare the medical history, the observation period, the instrument data, and the officer's own account of how the person appeared. Look for whether they agree.