How low carb diets can "trick" a DUI breath test

Some diets and medical conditions can cause the body to produce substances that are chemically similar to alcohol. These chemical substances are known as “ketones.”1

But DUI breath testing machines cannot always reliably distinguish between ketones and alcohol. Moreover, ketosis breath can smell like alcohol to police officers in the field. As a result, a DUI breath test can sometimes report a falsely elevated blood alcohol concentration (BAC).

Conditions that can cause the body to produce ketones include:

  • Diabetes,
  • Hypoglycemia,
  • Fasting, and
  • High-protein / low-carbohydrate diets (such as the popular Atkins and Paleo diets).

To help you better understand how medical conditions and diets can produce a falsely high BAC reading, our California DUI defense lawyers discuss, below:

1. What are ketones?

Ketones are chemical substances produced when the body burns fat as an energy source. They are similar in chemical composition to isopropyl alcohol. This is the type of alcohol found in solvents such as acetone.2

Isopropyl alcohol is not the same as ethyl alcohol, the type found in alcoholic beverages.3 But many DUI breath testing devices cannot reliably tell the difference. This is how DUI breath tests can be “tricked” by the presence of ketones.

How and why does the body produce ketones?

The primary source of energy for human bodies is carbohydrates. Carbohydrates are nutrients found in plant-based foods and dairy products. 4

When we eat carbohydrates, our digestive system breaks the digestible ones down into sugars, including glucose. Glucose is the body's main energy source. It is absorbed into the bloodstream after eating. For this reason, it is often called “blood sugar.”5

But if the body does not get enough glucose – or if it can't use glucose because of a lack of insulin --it burns stored fat instead.6

Unlike carbohydrates, stored fat cannot be broken down in the digestive tract. Instead, it must be broken down by the liver.7 This, in turn, creates “ketones,” which the body then burns instead of glucose.8

This is the body's normal protection against starvation. It is also a useful diet for athletes or others who need energy for strenuous workouts above and beyond the levels of glucose in their blood.

steak dui ketosis california legal defense
Steak is a popular keto-friendly meal choice

2. Low carbohydrate diets and other dietary causes of “ketosis”

One common cause of insufficient carbohydrate intake is high protein / low carbohydrates diets (such as the Paleo or Atkins diet). In this case, the production of ketones is intentional. By depriving the body of carbs, the body is forced to burn fat stores.9

Other causes of “ketosis” (high production of ketones) from too little carb intake include:

  • Anorexia,
  • Fasting,
  • Excessive vomiting,
  • Diarrhea,
  • Undereating, or
  • Starvation.10

3. Diabetes and ketones

Medical conditions such as diabetes can also result in an excess production of ketones. This occurs due to the body's inability to produce insulin—a hormone that helps the body burn glucose for fuel.11

After eating, the level of glucose in the blood rises. In a person without diabetes, the pancreas releases insulin. The insulin helps the liver and muscles store extra glucose. This, in turn, lowers the level of glucose in the bloodstream.

In people with diabetes, however, either the pancreas doesn't produce enough insulin (type 1 diabetes) or cells are less responsive to it (type 2 diabetes).12

As a result, the body can't use glucose for energy. Instead, it must burn protein and fat stores. This results in two things happening:

  1. Glucose builds up in the bloodstream, leading to dangerously high blood sugar levels, and
  2. The liver produces too many ketones for the body to fully eliminate, which can lead to a potentially life-threatening condition known as diabetic ketoacidosis (“DKA”).13

3.1. Diabetic ketoacidosis (“DKA”)

When ketone levels in the blood get too high, it can produce a serious condition known as “diabetic ketoacidosis” (“DKA”). Drivers experiencing DKA are especially prone to wrongful arrest for DUI as the symptoms of DKA can resemble those of alcohol impairment.

Common DKA symptoms can include:

  • Excessive thirst or dry mouth,
  • Frequent urination,
  • Sluggishness,
  • A flushed face,
  • Nausea and/or vomiting,
  • Confusion,
  • Decreased coordination, and
  • “Fruity” smelling breath that can be mistaken for alcohol.14

So someone suffering from DKA might not only “blow” a high BAC on a DUI breath test, he or she might appear drunk. Thus a law enforcement officer who is not a diabetes expert could easily arrest such a person for:

hypoglycemia california dui legal defense
When glucose levels become too low from hypoglycemia, they can have effects on the brain similar to intoxication from alcohol

3.2. How hypoglycemia can lead to a California DUI arrest

People with Type 1 diabetes take insulin or other drugs designed to lower blood sugar levels. But if they take too much insulin relative to the amount of glucose in the bloodstream, their blood sugar can drop too low, resulting in hypoglycemia.15

Bodies need a steady supply of sugar (glucose) in order to function properly. When glucose levels become too low from hypoglycemia, they can have effects on the brain similar to intoxication from alcohol.

Symptoms of hypoglycemia can include:

  • Confusion,
  • Inability to complete routine tasks,
  • Double or blurred vision
  • Heart palpitations
  • Shakiness
  • Anxiety
  • Sweating, and
  • Less commonly, seizures or loss of consciousness.16

Hypoglycemia in people who are not diabetic

True hypoglycemia is uncommon in people who do not have diabetes. But it can happen. Causes of non-diabetic hypoglycemia include:

  • Medications such as quinine, which is used to treat malaria,
  • Excessive alcohol consumption on an empty stomach,
  • Illnesses or disorders of the liver or kidneys,
  • Anorexia nervosa (or other long-term starvation),
  • Insulin overproduction from pancreatic tumors, and
  • Endocrine deficiencies.17

4. How ketones “trick” DUI breath testing devices

Excess ketones are excreted in the urine and breath.18 Not all DUI breath testing instruments are sophisticated enough to distinguish between ketones and blood alcohol content.19

As a result, ketones in the breath can fool some California DUI breath testing instruments. This means some people will test positive on a California DUI breath test even if they aren't actually drunk. Sometimes this even happens when they have not been drinking at all.

This can prove especially problematic when such people are also exhibiting visible symptoms of hypoglycemia or ketoacidosis.

5. Low-carb diet, diabetes or hypoglycemia as a DUI defense

It is important for people to tell their DUI defense lawyer if they have any medical conditions or are on a diet. An experienced attorney may be able to establish that the DUI breath tests were in error and the driver did not actually drive drunk.

Sometimes all this requires is the driver's medical records and a few witness statements. In other cases, it may require a DUI defense expert witness.

The point is that it is possible to challenge the results of a DUI breath test.

Often it will lead to the charges being reduced to the less serious charge of reckless driving. who can an experienced DUI attorney In some cases it can lead to the charges being dropped altogether.

And even if the case goes to trial, the defendant's medical history or diet might be enough to secure an acquittal. As Orange County DUI defense lawyer John Murray20 explains:

"Diabetes, hypoglycemia, and Atkins-style diets are just a few things that can mimic DUI. It's my job to make the jury understand that things aren't always what they seem when it comes to an alleged California drunk driving charge.”

california dui legal defense attorneys
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Wrongly charged with DUI in California? Call us for help…

If you were arrested for DUI and think your medical condition or diet may be to blame, we invite you to contact us for a free consultation.

Call us at 855-LAWFIRM to discuss your case confidentially with one of our experienced California DUI defense attorneys.

We have criminal law offices in and around Los Angeles, Orange County, San Diego, Riverside, San Bernardino, Ventura, San Jose, Oakland, the San Francisco Bay area, and several nearby cities.

We also have experienced Nevada DUI attorneys in our Las Vegas and Reno offices who represent clients accused of violating Nevada's DUI laws.

Legal references:

  1. WebMD, “What are ketones?”

  2. See also Alice and Fred Ottoboni, “Ketosis, Ketone Bodies, and Ketoacidosis: Modern Nutritional Diseases,” 2nd Edition, Chapter 8 (Lipids), February 20th, 2013 (“Excess ketone bodies are excreted by the kidneys and lungs. Exhaled acetone gives the breath a characteristic, sweetish odor.”).

  3. Healthfully, “What is the Difference Between Ethyl Alcohol and Isopropyl Alcohol?”

  4. Live Science, “What Are Carbohydrates?”

  5. Harvard School of Public Health, "Carbohydrates and Blood Sugar."

  6. Medical News Today, “Ketosis: What is ketosis?”

  7. University of California, San Francisco, “Ketones.”

  8. MNT.

  9. WebMD, “What is ketosis?”

  10. See WebMD, “What are ketones?”, endnote 1.

  11., “Diabetes and Ketones.”

  12. Mayo Clinic, “Diabetic Hypoglycemia.”

  13. Mayo

  14. Mayo

  15. Mayo

  16. Mayo

  17. Mayo

  18. Alice and Fred Ottoboni, endnote **.

  19. Lawrence Taylor, Drunk Driving Defense 3d Edition, page 685: “[I]sopropyl alcohol is virtually indistinguishable from ethanol in the infrared test chamber of the five-filter Intoxilyzer” [a type of California DUI breath testing machine].

    Same: "...the likelihood exists of auto-generated isopropyl alcohol upon the introduction of carbohydrates in the presence of ketosis and that the Intoxilyzer cannot dependably distinguish ethanol from isopropyl alcohol."

  20. Orange County DUI defense lawyer John Murray has been named one of the "100 Best" criminal defense attorneys by the National Trial Lawyers Association. He defends California DUI clients throughout Southern California, including in Orange, San Bernardino and Los Angeles Counties.

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