Fasting Diets and Breath Alcohol Testing

Examining issues with specificity & false positives

From Counterpoint Volume 8; Issue 3 - Article 1 (September 2024)

An article in the upcoming Foundational Skills I Course

Jan Semenoff, BA, EMA
​Forensic Criminalist

Article information:

Article - 2000 words (approximately 10 - 12 minutes)
It has long been held that the ketogenic diet may falsely elevate the reported results of a breath alcohol test. What effect will ketogenic conditions have on an electrochemical fuel cell? Will it introduce enough interferent chemicals or other sources of corruption in sufficient quantities to provide a false-positive reading?

The effect of fasting on the body

The fasting diet is designed to produce ketogenic conditions. When subject to fasting conditions, or an instability of blood glucose levels, the body will begin to metabolize stored fats, creating the medical condition Ketonemia. Ketone levels will then begin to rise in the blood and urine. This creates a situation where the person suffers from low blood sugar (becomes hypoglycemic) from a cause other than too much insulin. Ketosis can be smelled on a person’s breath and is commonly dismissed as alcohol consumption.
High blood sugar (Hyperglycemia)
In general, the signs and symptoms of Diabetic Ketoacidosis (medically referred to as Hyperglycemia) are like that of an impaired person:
  • There may be a musty, alcohol or unusual odor on the breath. It is often described as a “stale apple juice” or "fruity-smelling"odor.
  • The ability to follow directions may be affected, as impaired cognitive function is typical.
  • They may also display lowered levels of consciousness or confusion, heightened emotional states or extreme violence and belligerence.
Low blood sugar (Hypoglycemia)
Compare hyperglycemia with low blood sugar. Persons with Hypoglycemia will commonly experience extremely low blood sugar levels that will initiate ketotic hypoglycemia. When subject to this condition, the body will begin to metabolize stored fats. Ketone levels will then begin to rise in the blood and urine. This creates a situation where the person becomes hypoglycemic from a cause other than too much insulin. The Ketoacidosis can be smelled on a person’s breath and is often dismissed as alcohol consumption.
First Responders are taught that the signs and symptoms of each, although initiated by very different root causes, may be difficult to differentiate. Indeed, a standard way of teaching how to identify hyperglycemia in first aid courses is to describe the individuals “looking drunk” and hypoglycemia as the person “looking sick”. Additionally, the person experiencing low blood sugar may display:
  • Sweaty or pale appearance
  • Irritability or anxiety
  • Lack of loss of coordination or concentration, or the inability to complete routine tasks
  • Slurred speech
  • Sleepiness
  • Irregular or fast heart rate
  • unresponsiveness or loss of consciousness
​The first aid strategy when one cannot differentiate the symptoms is to give sugar as a fallback position, as it will immediately assist the hypoglycaemic patient by raising the blood sugar levels and will not appreciably harm the hyperglycaemic person.
Determining which blood sugar disorder is present
Symptomatic diagnosis is virtually impossible, with either blood glucose or blood ketone levels being the only accurate way to assess which condition is present. Ketone level measurement is emerging as the more accurate predictor of early-onset diabetic assessment. New technologies are emerging using breath analysis to measure the ketone levels.
When blood sugar levels drop, the body’s breakdown of glucose cannot provide sufficient energy, (through its main source of energy at the cellular level - Adenosine Triphosphate or ATP). The body’s metabolic pathway switches to Ketogenesis to provide an alternate energy source in the form of Ketone Bodies. At this point, ketone bodies replace blood glucose as a principal source of energy.
The initial situation for this hypoglycemic state is a rising level of ketones (Beta-Hydroxybutyrate in the blood that is first metabolized to form Acetoacetate, then Acetone which can lead to increased levels of Isopropanol).
It has long been known that the acetone is not a total waste product, being then converted into isopropanol through normal metabolism. This is an important step to consider. The alcohol produced, isopropanol, is NOT an alcohol that can be consumed safely by humans and is a toxic by-product of the ketogenic state.
Ketone body production depends on several factors, such as:
  • The individuals rate of energy expenditure at rest (known as the Basal Metabolic Rate, or BMR). Resting rates are used to eliminate the variable effect of physical activity,
  • Body Mass Index (BMI), and
  • Body fat percentage.
You may be interested to note that ketone bodies, which are considered a "super fuel," produce more ATP than simple blood glucose. If you compare energy production:
  • 100 grams of Acetoacetate generates 9,400 grams of ATP,
  • 100 grams of Beta-Hydroxybutyrate yields 10,500 grams of ATP, while
  • 100 grams of glucose produces only 8,700 grams of ATP.
​So, the ketone bodies actually produce more energy than simple sugars and enable the body to maintain efficient fuel production even when experiencing a low caloric intake.

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False positive breath alcohol testing results

The fuel cell component of breath testing devices are not immune to the effects of the ketone bodies and isopropanol on the reading obtained. The fuel cells are designed to identify the presence and concentration of ethanol. To a certain extent, all alcohols, and many other hydrocarbons, appear as ethanol to fuel cell instruments and can routinely report a falsely elevated BrAC reading. Keep in mind that Isopropanol is an alcohol.
The ketones were long known to affect chemical tests, such as employed in the original Breathalyzer. Infrared devices may or may not be affected, depending upon the wavelength used to detect ethanol.
Individuals following a ketogenic diet may experience a false positive breath alcohol test due to the conversion of acetone to isopropanol by the actions of the ADH enzyme (Alcohol Dehydrogenase) found in the liver, resulting in an inaccurate breath alcohol reading. (Masood, et al, 2023).
Bailey (1990) reported a patient presented at an emergency department who tested positive for isopropanol who was in fact in a ketogenic state, and who had not consumed any ethanol.
Laakso et al, (2004) studied the effect of various volatile solvents for potential interference with breath alcohol analysis using the Drager 7110 evidentiary breath analyzer which uses a fuel cell to determine the presence and concentration of ethanol. They concluded that acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, and diethyl ether did NOT significantly interfere with the fuel cells breath alcohol measurement, but both propyl alcohol and isopropyl alcohol had a significant effect during breath alcohol measurement using fuel cells.
In 2007, internationally noted toxicologist Dr. A.W. Jones (with S. Rossner) reported an instance of a false-positive breath test in a fuel-cell interlock device from a person on a ketogenic diet who was an absolute abstainer from alcohol. They also concluded that the increased levels of ketones, including acetone that is known to be bio transformed into isopropanol by the action of liver alcohol dehydrogenase as described above leads to this false-positive effect on the fuel cell device. They concluded that the side effects of the ketogenic diet warrant caution and further evaluation by authorities during breath alcohol testing.
In 2019 a case report was made to the publication Military Medicine regarding a sailor who reported for duty and was screened positive with a BrAC reading of 0.026 g/dL. He denied any consumption of alcohol, and was placed on duty as he was asymptomatic of impairment indicia. During his shift, under the watchful eyes of supervisors who confirmed zero alcohol consumption, his reported BrAC readings fluctuated from a low of 0.022 g/dL to a high of 0.048 g/dL. The sailor had previously lost about 55 pounds, which was attributed to his recent return from "an arduous submarine deployment". Both his blood glucose and A1c levels were very high, and he was subsequently diagnosed with diabetes.

The Blood-to-Breath (or Partition Ratio) and its impact on breath test results

All breath testing devices operate on the scientific principle that the amount of alcohol present in a breath sample is proportional to the amount of alcohol in the blood. This is known as the Blood-to-Breath Ratio (or commonly referred to as the Partition Ratio). The underlying rationale for this is a scientific principle known as Henry’s Law, which establishes that at a given temperature, the saturated vapor above a solution contains a concentration of solute proportional to the concentration of solute in the solution.
Breath testing devices used in North America are calibrated to a 2100:1 Blood-to-Breath Ratio; that is, when ethanol is considered, 2100 parts of ethanol measured in the breath is equal to one part of ethanol found in the blood. Every hydrocarbon compound that reacts with a fuel cell will have a different Partition Ratio.
What effect will this trace amount of Isopropanol provide?
The blood to air partition ratio for isopropanol has an accepted value of about 1370:1. The blood to breath ratio for ethanol has been legislatively accepted at 2100:1. Therefore, any trace levels of isopropanol found within the body would have an exaggerated effect on the readings obtained on a device calibrated at 2100:1. It has also been reported that blood levels of isopropanol have a tendency towards very low elimination rates in the body (Jones, 1996).
Acetone amounts are even more volatile, with a reported blood to air partition ratio of about 130:1. This is considered extremely high when compared to many other volatile organic compounds. It has long been recognized that small amounts of acetone are also endogenously produced in the human body and a by-product of normal fat metabolism. (Wagaeus et al, 1981).
Therefore, even trace amounts of acetone in the breath of a test subject will have a profound effect on the breath reading, as the breath testing device is calibrated to believe 2100 parts are present when read, rather than the actual level of 130 parts. In other words, a trace amount of acetone will be considered to produce an effect more than 15 times that of ethanol. 
It has been identified by various researchers that certain hydrocarbon compounds, including isopropanol and acetone, cause inflated breath alcohol readings on various breath testing devices that are often not detected by the testing devices themselves (Hak, 1995, Jones et al, 1996, Caldwell & Kim, 1997, Bell et al, 1992, Logan et al, 1994 and Memari, 1999).

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The period of time over which Ketosis can affect breath tests

It should be noted that once a ketogenic diet, or fasting conditions have begun, the measurable levels of acetone in the breath rise steadily, increasing exponentially over the first 2-3 days, and after a week or so, achieve a consistent elevated state. Fasting conditions can produce levels of acetone in the breath that exceeds that of diabetics suffering from ketoacidosis. Until the person consumes a high calorie or high carbohydrate meal, their breath acetone levels are considerable.
More importantly, studies indicate that these levels remain high before they begin to drop to baseline levels after consumption of a fairly significant amount (about 500 calories) at a minimum. A protein rich meal will return a person to baseline levels within 5-6 hours, and a heavy meal will return a prolonged fast to baseline values within 16 hours. (Anderson, 2015).
A rise in blood glucose levels does not immediately create a reduction in endogenous acetone, as the blood sugars must be processed by the naturally occurring insulin in the pancreas before ketone bodies are metabolized, and this takes a number of hours to occur once the blood glucose levels are replenished. As such, the recent introduction of sugars into the system does not immediately correlate to a reduction of endogenous breath ketone levels.

Verifying the false positive effect

In 2016 I was asked to reproduce the results of an experiment performed by the Laboratoire de sciences judiciaires et de medecine legale – Quebec. This involved a gentleman in a state of ketoacidosis. The results of my experimentation indicate that the fuel cell device, in this case an Alco-Sensor FST generated additive results with a false-positive reading between 0.053 – 0.100 g/dL higher than the true value in the presence of the acetone and isopropanol produced by a ketogenic diet. Falsely adding 0.10 g to a reported breath reading is highly significant.
It should be noted that my experimentation was performed in vitro, using an alcohol simulator with a simulator solution of a known ethanol concentration. It is the action of the volatile organic compounds (VOCs) on the fuel cell that produces the false positive effect regardless of its source.
As with false positives generated by recent consumption (the so-called mouth alcohol effect), any VOCs present on the breath of the test subject will be additive to any underlying blood alcohol concentration.

Final thoughts:

I am left to reasonably conclude, as have other researchers, that a combination of substances in the fuels cell may falsely over-report the true BrAC level, even if that true value is zero. It should be noted that none of the fuel cell devices currently available have the capability of incorporating an interferent detector algorithm or component to screen for interferent chemicals in their reported analysis for BrAC levels. It is simply beyond the capability of the fuel cell technology. 
As such, persons fasting who have created situations of uncontrolled blood ketone or blood glucose levels are extremely poor candidates for breath alcohol testing. Their reported BrAC readings may be adversely affected by VOC's found endogenously on their breath, and may not be a reliable reflection of their true Blood Alcohol Concentration, if any.
​Practice Tip:
You need to add a section on medical history and dieting into your client intake interview. 

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For further study:

  1. Anderson, Joseph C., Measuring Breath Acetone for Monitoring Fat Loss: Review, Obesity. 23(12):2327-2334, December 2015.
  2. Bailey, D., Detection of Isopropanol in Acetonemic Patients Not Exposed to Isopropanol, Clinical Toxicology, 28(4), 1990, Pages 459-466.
  3. Bell, C. M. and Gutowski, S. J. et al, Diethyl Ether Interference with Infrared Breath Analysis, Journal of Analytical Toxicology, Vol. 16, pp. 167-168, May/June 1992.
  4. Caldwell, J, and Kim, N., The Response of the Intoxilyzer 5000® to Five Potential Interfering Substances, J. Forensic Science 1997;42(6) pages 1080-1087.
  5. Hak, E.A., The Effects of Volatile Substances on the Intoxilyzer 5000C Breath Testing Instrument, Royal Canadian Mounted Police Forensic Laboratory, Peer-Reviewed Paper for the Traffic Safety 1995 Conference, 1995.
  6. Jones, A.W., Andersson, L., Biotransformation of Acetone to Isopropanol Observed in a Motorist Involved in a Sobriety Check, Journal of Forensic Sciences, JFSVA, Vol. 40, No. 4 July 1995, Pages 686-687
  7. Jones, A.W. & Summer, R., Detection of Isopropyl Alcohol in a Patient with Diabetic Ketoacidosis, The Journal of Emergency Medicine, Vol. 19, No. 2, 2000, Pages 165-168.
  8. Jones, A.W., Interfering Substances Identified in the Breath of Drinking Drivers with Intoxilyzer 5000S, Journal of Analytical Toxicology, Vol. 20, November/December 1996, Pages 523-527.
  9. Jones, A.W. & Rossner, S., False-Positive Breath Alcohol Test After a Ketogenic Diet, International Journal of Obesity, (2007) 31, Pages 559-561.
  10. Jones, A.W., Observation on the Specificity of Breath Alcohol Analyzers Used for Clinical and Medicolegal Purposes, Journal of Forensic Sciences, JFSCA, Vol. 34, No. 4, July 1989, Pages 842-847.
  11. Laasko, O., Pennanem, T., et al, Effect of Eight Solvents on Ethanol Analysis by Draeger 7110 Evidential Breath Analyzer, Journal of Forensic Science, Sept 2004, Vol 49, No. 5.
  12. Logan, B, Gullberg, R. and Elenbaas, J., Isopropanol Interference with Breath Alcohol Analysis: A Case Report, J. Forensic Science 1994 Jul:39(4), pages 1107-1111.
  13. Masood W, Annamaraju P, Khan Suheb MZ, et al. Ketogenic Diet. [Updated 2023 Jun 16]. National Library of Medicine, available at: https://www.ncbi.nlm.nih.gov/books/NBK499830/
  14. Memari, B., Variables Affecting the Precision and Accuracy of the Intoxilyzer 5000, Florida International University, Thesis for Master of Science in Chemistry, academically reviewed and approved, 1999.
  15. Norfold, G. & Quartly, C., Volatile Substances and their Potential to Interfere with Breath Alcohol Reading Instruments, Journal of Clinical Forensic Medicine (1997) 4, Pages 21-23.
  16. Platteborze, P. L., Rainey, P. M. and Baird, G. S., Ketoacidosis with Unexpected Serum Isopropyl Alcohol – Clinical Case Study, Clinical Chemistry 57:10, 1361 – 1365 (2011).
  17. Reinhart, J., Early Detection of Diabetic Ketoacidosis by Breathalyzer in a Sailor Reporting for Duty, Military Medicine, Vol. 184 Nov/Dec 2019.
  18. Wigaeus, E, Holm, H and Astrand, I., Exposure to Acetone – Uptake and Elimination in Man, Scand. Journal of Environ Health, 7 (1981) 84-94.