A medical condition can matter in a Montana DUI case, but rarely in the way online articles claim. No diagnosis cancels a breath result on its own. What a condition can do is explain the signs an officer took for impairment, or in specific circumstances raise a real question about a breath sample. Either way it has to be proved. This page is part of our Montana DUI Guide. We are lawyers, not physicians, and the medical descriptions below come from the federal health sources named.
Two Different Problems
It helps to separate them.
- Symptoms that look like impairment. This goes to the impairment charge, which requires proof that your ability to drive safely was diminished by alcohol or drugs (MCA § 61-8-1002(1)(a)). If a medical condition explains the stumbling or the confusion, that proof is weaker.
- Something that affects the breath sample. This goes to the number. It is a narrower argument and needs more support.
Conditions That Come Up, and What Is Documented
| Condition | What health sources say | What is argued in a DUI case |
|---|---|---|
| Acid reflux (GER or GERD) | Stomach contents come back up into the esophagus (NIDDK). | That alcohol from the stomach reached the mouth just before the sample. |
| Diabetes with ketoacidosis | The body produces ketones, and breath can smell fruity (MedlinePlus). | That the odor was mistaken for alcohol, or that a device reacted to something other than alcohol. |
| Low blood glucose | Shakiness, dizziness, confusion, and trouble seeing or speaking clearly (NIDDK). | That the symptoms an officer recorded were medical, not alcohol. |
| Very low carbohydrate or keto diet, fasting | Blood ketone levels are higher than usual (MedlinePlus). | The same interference argument made in diabetes cases. |
| Dentures and dental work | The Montana rules we read do not mention them. | That alcohol was held in the mouth longer than usual. |
The middle column is established medicine. The right column is advocacy. The distance between them is what a case has to cover with evidence.
Reflux and the Mouth Alcohol Argument
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) describes gastroesophageal reflux as stomach contents coming back up into the esophagus, and GERD as a more severe and long-lasting form. In a DUI case the claim is that this carried alcohol into the mouth shortly before the breath sample, which is the mouth alcohol problem.
Montana courts have heard the argument. In State v. Levanger, 2015 MT 83, the driver said he could have regurgitated on the way to the station. The Court upheld the breath result, noting that the trooper saw no sign of it and that the argument "amounts to a hypothetical without any factual basis" (¶ 14). A diagnosis in your chart before the arrest, a prescription history, and video showing an episode would each move the claim away from hypothetical.
Diabetes, Ketones, and Low Blood Glucose
Diabetes shows up in DUI cases more through symptoms than through chemistry. NIDDK's list of low blood glucose symptoms includes feeling shaky or jittery, dizzy, lightheaded, confused, or irritable, and being unable to see or speak clearly. An officer at a dark roadside may record those as signs of alcohol.
The chemistry argument concerns ketones. MedlinePlus, from the National Library of Medicine, explains that ketones are acids the body makes when it breaks down fat for energy, that diabetic ketoacidosis can cause fruity-smelling breath and decreased alertness, and that a ketogenic diet raises blood ketone levels. NHTSA's officer training manual says some preliminary breath test devices "might react to certain substances other than alcohol," and names acetone among its examples.
That statement is about roadside screening devices, not the station instrument. For the station instrument, Montana's rules require a laboratory certification, valid for 365 days, that includes "a review of the breath analysis instrument's sensitivity for the detection of interfering substances" (ARM 23.4.214(1)(d)). We have not found a Montana Supreme Court decision holding that ketones caused a false evidentiary result. That is a reason to treat the claim carefully, not a reason to ignore a documented medical episode.
Dental Work and Dentures
The idea is that dentures, bridges, or recent dental work hold alcohol in the mouth longer. The Montana breath testing rules we read (ARM 23.4.201 to 23.4.225) say nothing about dental appliances, and we have no agency source to cite on how much difference they make. If this applies to you, tell your lawyer and check whether the officer asked about it or looked in your mouth before the test.
What Montana Law Lets You Do
- Say it on camera. Telling the officer about a condition creates a record at the time. You are not required to answer questions, but a medical fact stated plainly is hard to dispute later.
- Ask for an independent blood test. You pay for it, a physician or registered nurse must draw it, and the officer may not unreasonably impede it but has no duty to drive you (MCA § 61-8-1019(2)).
- Get the test records. Full information about any test given at the officer's direction must be made available on request (MCA § 61-8-1019(3)).
- Rebut the inference. In an impairment case, the inference from a 0.08 result is rebuttable (MCA § 61-8-1002(2)(c)).
One caution. Refusing a test because of a medical worry has its own consequences, including a license suspension with no probationary license. See test refusal in Montana.
What It Takes to Prove
A judge or jury will want more than a diagnosis. Useful evidence includes treatment records that predate the arrest, glucose meter or monitor data from that day, pharmacy records, the video, and testimony from a treating provider or a qualified scientist who can connect the condition to what happened. Conditions also matter for the field sobriety tests, where balance, vision, and injury are directly relevant. How this fits with the rest of a defense is covered in challenging the breath test and DUI defenses.
This page explains Montana law in general as of the 2025 Montana Code Annotated and the Administrative Rules of Montana. Medical descriptions are summarized from NIDDK and MedlinePlus and are not medical advice. It is not legal advice about your specific case.