Certain medical conditions can cause breath tests to read incorrectly, which is bad news if you’re being tested by the police. Even if you say you haven’t been drinking, a reading showing intoxication can quickly land you with an arrest.

In one recent story, a man blew a breath test for the authorities and had it come back well above the limit, even though he hadn’t been drinking and seemed otherwise fine. Interestingly, the case ended up being dropped, because the man was in ketosis at the time of the test. Being in great shape, the fact that he was in ketosis actually caused the breath test to give a false positive. Why? Ketosis causes the liver to break down fat for fuel, creating acetone. Some of that acetone is released as isopropyl alcohol in your breath.

Other medical conditions can affect breath tests, too. Diabetes is known to cause false positives for similar reasons. Acid reflux may also do the same.

What should you do if you’re stopped and accused of drinking and driving despite not having done so?

You should ask if you can go back to the station for a different test. Blood tests can be a good go-to if you know that you don’t have any drugs that could affect the test in your system.

You can also reach out to your attorney with information on your medical state that could help with your defense. If there is a reason for a false positive, your attorney can help you fight against the DUI that you’re facing.