Low Carb Diet, Ketones & DUI Breathalyzer – A Legal Guide

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

However, 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 result can sometimes report a falsely elevated blood alcohol concentration (BAC).

Conditions that can cause your 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 false positives for high BAC readings, our California DUI lawyers will discuss:

• 1. What are ketones?
• 2. Does a low carbohydrate diet cause “ketosis”?
• 3. How does diabetes affect ketones?
  • 3.1. Diabetic ketoacidosis (“DKA”)
  • 3.2. How hypoglycemia can lead to a California DUI arrest
• 4. What is ketones’ effect on the DUI breathalyzer?
• 5. How can these issues help me fight a DUI case?
• Additional resources

1. What are ketones?

Ketones are chemical substances produced when your 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 However, 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 you eat carbohydrates, your digestive system breaks the digestible ones down into sugars, including glucose – the body’s main energy source. It is absorbed into the bloodstream after eating. For this reason, it is often called “blood sugar.”⁵

Though if your body does not get enough glucose – or if it cannot 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 your body then burns instead of glucose.⁸

This is your 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.

2. Does a low carbohydrate diet cause “ketosis”?

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

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

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

3. How does diabetes affect ketones?

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

After eating, the level of glucose in your blood rises. If you do not have diabetes, your pancreas releases insulin. The insulin helps your liver and muscles store extra glucose. This, in turn, lowers the level of glucose in your bloodstream.

If you have diabetes, however, either:

• your pancreas does not produce enough insulin (type 1 diabetes) or
• cells are less responsive to it (type 2 diabetes).¹²

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

1. Glucose builds up in your bloodstream, leading to dangerously high blood sugar levels, and
2. The liver produces too many ketones for your 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 your blood get too high, it can produce a serious condition known as “diabetic ketoacidosis” (“DKA”). If you are experiencing DKA, you 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 if you are suffering from DKA, you might not only “blow” a high BAC on a DUI breath test, you might appear drunk. Thus a law enforcement officer who is not a diabetes expert could easily arrest you for:

• Driving under the influence of alcohol – California Vehicle Code 23152(a),
• Driving with a BAC of .08% or greater – California Vehicle Code 23152(b),
• Commercial driver DUI (BAC of .04% or greater) – Vehicle Code 23152(d),
• Taxi, limo or ride-sharing driver DUI (.04% or greater) – Vehicle Code 23152(e), or
• Underage DUI (BAC of .05% or greater) – California Vehicle Code 23140.

3.2. How hypoglycemia can lead to a California DUI arrest

If you have Type 1 diabetes, you take insulin or other drugs designed to lower blood sugar levels. Though if you take too much insulin relative to the amount of glucose in your bloodstream, your 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 your 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 if you 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. What is ketones’ effect on the DUI breathalyzer?

Excess ketones are excreted in your 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 your breath can fool some California DUI breath testing instruments. This means you may test above the legal limit on a California DUI breathalyzer test even if you are not actually drunk. Sometimes this even happens when you have not been drinking at all.

This can prove especially problematic when you are also exhibiting visible symptoms of:

• hypoglycemia or
• ketoacidosis.

5. How can these issues help me fight a DUI case?

It is important for you to tell your DUI defense lawyer if you have any medical conditions or are on a diet. An experienced attorney may be able to establish that:

• your DUI breath tests were in error and
• you did not actually drive drunk.

Sometimes all this requires is your 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. Sometimes it will lead to your charges being reduced to the less serious charge of reckless driving. In some cases, it can lead to your charges being dropped altogether.

Even if the case goes to trial, your 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.”

Additional Resources

For more in-depth information, refer to these scholarly articles:

• Flawed Blood Tests: The DUI Exception to Admissible Evidence – Albany Law Journal of Science and Technology.
• Endogenous Ethanol ‘Auto-Brewery Syndrome’ as a Drunk-Driving Defence Challenge – Medicine, Science, and the Law.
• False-positive breath-alcohol test after a ketogenic diet – International Journal of Obesity.
• The Auto-Brewery Syndrome: A Perfect Metabolic “Storm” with Clinical and Forensic Implications – Journal of Clinical Medicine.
• Understanding Auto-Brewery Syndrome in 2023: A Clinical and Comprehensive Review of a Rare Medical Condition – Cureus.

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