Monitoring Nutritional Ketosis

We are inherently fat burners. We carry with us abundant stores of this fuel in the form of triacylglycerides or triglycerides, perhaps 50,000 or 100,000 Cal of fat energy.  We have evolved to process carbohydrates (sugars) in order to use this energy source but  we can only store a couple thousand Cal of this energy as liver and muscle glycogen and only a few hundred as blood glucose.  After we fill that tank, de novo lipogenesis must occur and begins to do so in a harmful way, leading to the carbohydrate poisoning and manifestations of the ‘metabolic syndrome’.

Burning fat is a clean, high energy process that begins with beta oxidation of fatty acids to produce Acetyl-CoA. Acetyl-CoA can come from other substrate metabolism as well.

Screen Shot 2017-08-12 at 3.20.40 PM.jpg

BOHB is not truly a ketone but a reduced form of acetoacetate and it is in equilibrium with acetoacetate in the blood. Acetone is decarboxylated acetoacetate and is not used directly as an fuel source but can, through conversion to lactate, then acetyl-CoA, be put back into the TCA cycle. Severe lactic acidosis and ketoacidosis are hallmarks of the total lack of insulin found in type I diabetics who may develop this condition. This should, of course, never be confounded with the normal physiologic ketosis of primary fat metabolism which is not only well tolerated but is our most effective and healthy form of energy.

Blood Alcohol Monitors

These inexpensive breath monitors are designed to detect the level of ethanol in the breath.  Fortunately for those wanting to monitor ketosis, these sensors detect a variety of volatile solvents, one being acetone, a volatile degradation product of ketone bodies.

This gives us access to an inexpensive ketometer.

These inexpensive monitors use the TGS 822 and other similar organic solvent vapor monitors

Shown above, the ‘chip’ functions as a variable resistor and can be implemented in one fashion in a voltage divider circuit with another resistor, designated R0 in the diagram below.  What we would like to see would be a steep curve for the best sensitivity.  Acetone is shown in red (diagram from and is pretty much on par with the curve to EtOH, but I suppose the ethanol vapors we typically deal with have a wider range than those of physiologic breath acetone vapors*.  More on that below.

The MQ303B is another solvent sensor that is priced at well under $1.

Under construction – but here are cheap monitors, one from Walmart, the others from Amazon, all $9 -$20

I’m pointing out the variability I’m seeing in response.  I’m thankful for a ‘cheap’ monitor.  Keep in mind that the software and scaling resistors on these monitors are designed for bigger resistance swings for ethanol measurement, thus we are dealing with statistically poor resolution at the bottom of the measurement range.  It’s like someone driving a car beside you and trying to measure your running speed off the speedometer.  They can tell you that you are moving.

More on this later from

These diagrams from the above study are from a study done of individuals both fasted and on a ketogenic diet.  Measurements are done with some very precise chromatographic and analytic equipment for measuring both the two blood ketones and the precisely sampled breath ketones (chromatograph).  In spite of this, note the curves that compare breath acetone to the two ketones.  R is around 0.54

Screen Shot 2017-08-12 at 3.46.02 PM.jpgScreen Shot 2017-08-12 at 3.46.09 PM.jpg

Here are three simultaneous readings from my three breath alcohol (BAC) monitors.



Amazon #1


Amazon #2


Some points I’m getting from this

  • Even under a system of precise measurement, blood ketones and breath acetone correlation may not be very precise
  • Cheap ethanol breathalyzers probably miss low and possibly therapeutic blood ketone levels as their hardware and software are scaled for ethanol measurement
  • Different brands seem to be a bit off, not only because of their resolution but perhaps also in scale.  Amazon #2 always gives me higher reading.  I like this because it might detect acetone at a lower level but I haven’t confirmed this. I may collect some data from the three over a few days to put more statistical significance in this

In addition, the data may be out there somewhere that I’m unaware of, but we I don’t think we have a dose-response curve for ‘nutritional ketosis’ however we define it. We may not even be quite sure of the response we are looking for. We may be experimenting as we rediscover this clean and more healthy source of metabolic fuel.

Be thankful for these cheap BAC monitors!  This hack is a serious asset for those hitting the ultra low carb scene.  I will probably get a more precise breath ketone monitor soon to report on.

Being an EE, I can’t wait to build my own but I got a lot of projects pending.

My three day experience with the limited ability of the BAC monitor has shown me that it is not only important in achieving / verifying the ketosis but it provides incentive for maintaining it’s dietary components. It provides insight into the benefits and interaction of exercise on the ketotic state.

8/13 – rebreathing may improve accuracy – more on this later


In case you might be worried that breath ketones might get you a false positive DUI reading . . .

IR (Infrared) ethanol meters used by law enforcement for evidential purposes are generally insensitive to breath acetone levels:

They use an IR optical bench to single out EtOH absorption over other volatile agents and the just about totally reject acetone when reading the EtOH signature.

I work at a public hospital with high ambient law enforcement level.  I’ll see if they can give me a breath test side by side with my cheap breathalyzer and get back to you.



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