Keto Breath Testing: Is it Accurate?

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I really got into the discussion about keto breath testing about six months after I started the keto diet. Over the past few years I've been researching and testing a variety of ketone testing methods.

This post is a collection of my research, thoughts and experience with testing for ketosis. I'll be updating this post regularly as new information becomes available. If you have any sources for me, please post those in the comments.

First, this post assumes that ketone test strips are not a good measure of ketosis past the first few weeks. In fact, I wouldn't even bother spending the money on urine strips. These strips test whats coming OUT of our body. They are a fun tool the first few weeks, but after that, we hope our body gets used to using ketones for energy and the strips are no longer useful because there will naturally be less ketones in our urine…not because we aren't producing them…but because we're using them!

Ketone Blood Tests

While ketone blood tests ARE an excellent way to test your blood level for BHB (beta hydroxybutyrate) they come with a higher price tag.

We personally use both methods, testing blood levels on a weekly basis or when testing a new product (food or ketone tester).

Many of our tribe tell us that they don't want to have to prick their finger to get a ketone measurement and I completely agree. While Jeremy doesn't mind pricking his finger, I certainly don't look forward to the process.

Blood Tests vs. Breath Tests

Blood tests and breath tests measure different things.

Blood tests measure Beta Hydroxybutyrate in the blood.

Breath tests measure acetone, which is a metabolic waste product we breathe out when we are in a state of Ketosis.

Are Ketone Breath Tests Accurate?

Ketone breath tests measure acetone which is a by-product of the fat metabolism process.

The big question… Is this an accurate measure of ketosis in the body?

Research tells us YES.

It has been well established over the last 50 years that acetone in the blood and breath increases with fasting and calorie restriction. In the past 25 years there have been multiple studies quantifying the relationship and relating Acetone (BrAce) to Beta Hydroxybutyrate levels in the blood.

You can find a review of these studies here. See figure 2 of the study for a very interesting chart showing the relationship between acetone & bhb.

Review: KetoScan Mini

The KetoScan Mini is a high quality breath ketone measurement device manufactured by a company who has been providing law enforcement with accurate breathalyzers for over 20 years.

Most of the products on the market have cheap sensors in them that can be easily influenced by hydrogen or other gasses in the air.

Because a high quality sensor requires re-calibration from time to time, the KetoScan mini features a self-diagnostic mode. This is simply the device's re-calibration mode when it has sensed gases or other airborne smells in the air. In order to minimize the appearance of self-diagnosis mode, store your KetoScan Mini in a place where you aren't cooking, using personal care products or having other smells. Or, just expect to see self-diagnosis mode most of the time.

How To Test With KetoScan Mini

In my video above, I demonstrate how to use the KetoScan Mini.

First, you'll want to download the KetoScan app to your phone or tablet. Pair your KetoScan mini with your phone and proceed through the onscreen instructions.

When you test, make sure you take a normal breath. It is intuitive to take a very deep breath before blowing into the device and it may take a little practice to just take a normal breath.

Once prompted, you'll blow into the device for three seconds using pretty good pressure. Try to maintain consistent air pressure during the entire blowing process. Also try to blow with the same pressure each time you test for consistent results.

Your result will show you:

  • Your Acetone level in PPM. Optimal level is 10ppm.
  • Your body fat burning rate
  • A message indicating your level of ketosis
  • A button to push to enter any comments you have or food pictures if you are taking those throughout the day

The app will store your measurements over time so that you can refer back to where you were during different times. We find this a very useful feature.

Resources & Additional Reading

Anderson, Joseph C. “Measuring breath acetone for monitoring fat loss: Review.” Obesity (Silver Spring, Md.) vol. 23,12 (2015): 2327-34. doi:10.1002/oby.21242

Güntner AT, Kompalla JF, Landis H, Theodore SJ, Geidl B, Sievi NA, Kohler M, Pratsinis SE, Gerber PA. Guiding Ketogenic Diet with Breath Acetone SensorsSensors. 2018; 18(11):3655.

Kathy Musa-Veloso, Sergei S Likhodii, Stephen C Cunnane, Breath acetone is a reliable indicator of ketosis in adults consuming ketogenic meals, The American Journal of Clinical Nutrition, Volume 76, Issue 1, July 2002, Pages 65–70,

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