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How To Use the Ketonix Breathalyzer

A few months ago, I received my first keto breathalyzer and would like to share my thoughts on this device. The creator of the Ketonix breathalyzer, Michel Lundell, also runs a website to help and support people who use the device for measuring their ketone levels. The price of Ketonix is $ 149 (or $ 169 with the battery).

You can buy the Ketonix breathalyzer at I was given this device free of charge and I'm not affiliated with Ketonix. The opinions expressed and photos in this post are my own.

Measuring Ketones in a Nutshell

Before I get to details of how to use the Ketonix breathalyzer, I'd like to start with some basic facts. There are 4 ways to measure your ketone levels:

  • Ketostix. It measures urinary ketones (acetoacetate), is inexpensive but inaccurate because it only measures "wasted" ketones in your urine. In fact, once you get keto-adapted, you may not be able to measure any.

  • Blood Ketone Meter. It measures beta-bydroxybutryate (BHB) and is the most accurate method of measuring ketones (although BHB is not technically a ketone). The drawback is that the strips are fairly expensive, especially if you measure frequently.

  • Observation and following a healthy ketogenic diet. In my opinion, if you don't follow a keto diet for therapeutic purposes (or for performance enhancement), you don't need to measure your ketone levels. In fact, you don't need to follow a very low-carb diet to lose weight. What matters is finding your personal carb intake and also consider other factors that I explained here.

  • Breathalyzer (Ketonix). It measures acetone (acetone is made from a break down of acetoacetate). It's great value for money as it's a one-off payment, there is no need to buy expensive strips and it's accurate enough to tell you whether or not you are in nutritional ketosis and give you an approximate measure of how your ketone levels fluctuate. It will also give you idea of how certain foods affect your ketone levels.

Keep in mind that ketone levels will not tell you how much fat you've been burning. Don't worry if you never measure high ketone levels with any of the above methods. There is no evidence that more ketones will help you lose more weight. High ketone levels have therapeutic uses in epilepsy, Alzheimer's and cancer, or may benefit athletes.

In my review, I'm not going to focus on the correlation of blood ketones and breath ketones (here is a review focused on that). Instead, I focus on how to use this device. The reason I decided to do that is that I found the user interface quite challenging. The good news is that the people behind the device are planning to add several new features, including a wizard that will guide you through the process of measuring your ketones.

How to Use the Ketonix Breathalyzer

1. Create an Account at Ketonix and Download the Software

First, you'll need to create an account at Once you create an account, you can download the Ketonix software for Mac or Windows in My Menu -> Downloads.

2. Setup the Ketonix Software

The first time you use the device, it may take up to 30 minutes to get it ready for measuring. Connect your Ketonix into your computer via the USB port. Once you plug the Ketonix into your computer, it will start Initializing (see step 4 for more information on what it means).

3. Create a Profile

All measurements you take will be recorded against a user profile. To create a profile, go to File -> Profile -> click on the "+" button on the bottom left. Enter your Profile Name and choose where you want your data saved on your computer by clicking on the browse button. Enter the File Name and add the .csv extension (I named mine "MartinaKetonix.csv").

Enter the Username and Password for the account you created at Optionally, select Gender, Age and Usage. Click on Create Profile and click on Verify. Verify will link your local account to your Ketonix account. You can only verify once you have entered the correct username and password. Then click Close.

4. Initializing

Initializing is the process of preparing the device for measuring. For day-to-day readings, you have to wait until the device is initialized before you take any readings. If you are setting up the device for the first time and going through steps 1-3 your device should be initialized by now. In any case you have to make sure you have to wait until intitialization is complete - the light on your Ketonix will stop flashing.

What does initializing do? The sensor needs power to heat up every time you plug it in your computer.

5. Calibration

Before you start using your Ketonix, you have to calibrate it. To do that, go to File -> Calibration and click Start. Wait until the calibration is finished. It will take several minutes so be patient.

Why calibrate? The calibration sets a reference value making readings consistent. Each environment (temperature, pressure) is different. Also, using the device over time will affects readings. You only need to do this once unless you change environment or haven't used your breathalyzer for a long time. The value displayed should be close to zero once the calibration is done.

6. You are Ready to Measure

Make sure you select the right Profile before you measure (Select Profile -> your profile) and that the initializing process has finished.

On the side of the mouthpiece, you'll notice there is a small hole. There is a corresponding one on the device and they have to line up precisely. If they are not aligned, you won't be able to exhale into the breathalyzer and take a measurement.

To take a measurement, first click Start and then start blowing into the breathalyzer. To do that, breathe as normal (do not take a deep breath). Blow for about 15 seconds or as long as it feels comfortable.

7. Save the Results

Remove the breathalyzer from your mouth and wait for the readings to settle. This may take up to 30 seconds (mine take no longer than 10 seconds). After measuring, keep the Ketonix plugged in for another minute to eliminate moisture in the sensor. Then, keep in in a box to avoid dust getting in the sensor. If you want to take another measurement, wait until the blue light is not flashing.

As soon as you see the "Time to click on Stop & Save?" message, click Stop & Save. The results will be saved on your computer on the location you specified when you created your profile.

8. Preview Your Results

While taking a measurement, the Ketonix will also indicate your ketone levels using different colours on the device (blue for no or very little ketones, green for small amounts, yellow for moderate and red for high). The new Ketonix model also indicates the level by flashing (1 flash means the lowest concentration and 10 flashes represent the highest value).

Your results will also appear online at (My Menu -> Ketonix Charts) - just click on the chart to see a larger version. You can also access the online results directly from your computer (View -> Charts). I've been told that there will be offline (local) charts in the next release.

Additional Tips

Using a Battery

If you are travelling, you can use the optional battery. This allows you to quickly check your average ketone levels. The drawback is that you won't be able to save your measurement.

Always make sure you charge the battery, ideally overnight, before using with the breathalyzer. The blue light will be flashing while the device is initializing. Wait until the light stops flashing and then blow into the breathalyzer (again for about 15 seconds). After you finish blowing, give it a few seconds. In the new model I tested, the blue light will change and it will start flashing (1-10 times). The consecutive quick flashes are the ones you want to count although you don't have to as the colour itself will give you an indication of your ketone level: blue (none), green (low), yellow (moderate) or red (high) light.

How to Get Best Results

Keep the measuring consistent. Ketone levels are typically low in the morning and increase during the day with the highest levels before bed. It doesn't matter when you measure but the rule is that you should measure at the same time of a day to get the most consistent data. During my experiment, I measured twice a day (noon and evening) - thus the fluctuations.

Food intake. When and what you eat will also affect your ketone readings. Keep that in mind and don't be surprised when you see fluctuations.

Alcohol consumption. Do not drink alcohol before measuring. Since the Ketonix measures acetone, you won't get accurate readings and your values will appear artificially high.

Try to exhale for the same period of time. The longer you exhale, the higher the ketone readings may appear. It's good to stick with the same time - like 15 seconds every time you measure.

Which Model to Choose

There are two types of the Ketonix breathalyzer - the old and the new model. The main difference is that the new version provides more accurate data when not using a computer. The new model indicates 1-10 flashes for each level - blue, green, yellow and red. It costs $ 149 without the battery and $ 169 with the battery - the old model is $ 75. To see which ones they are, go to

The new models (both Red and Blue) are pre-configured to different ranges. The Blue defaults to the "Standard" range while the Red defaults to the "Sport" range. You can always reconfigure these ranges on your computer - see below.

Setting Your Custom Levels

Finally, apart from using default levels for ketone readings, you can change them in Settings. By dragging the knobs for green, yellow and red, you can easily set ranges. I didn't change these values and kept the device at the default levels.

According to Ketonix, anything between 40-70 is regarded as nutritional ketosis but this may vary for individuals. The official website advices to use a one-day water fast to find your minimum and a 3-day water fast to find your maximum. I'm not convinced this is something you need to do so I just used the default values. If you decide to do that, make sure you consult this with your doctor. Pregnant women and people with health conditions like diabetes, hypoglycaemia and those with eating disorder history should avoid fasting.

How about you? Do you monitor your ketone levels? Which method have you been using and what is your experience?

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Please, note that I do not offer personalised advice. For personalised advice you can contact one of our experts.

Comments (36)

Excellent article. You might also be interested in this article that describes how to  convert the Ketonix Value into a more standard PPM value:


That's useful, thank you!


I have and use a Ketonix.  You are correct that the company's website leaves something to be desired.  Also note that as soon as you hit "Start" - you must wait as the various colors appear on the breathalyzer and it turns back to blue before you start your sample.  
I started using the Ketonix while on Ideal Protein protocol - I was clearly in ketosis (after I figured out all the nuances of using the Ketonix that really aren't addressed by the company.)
Now I eat pure ketogenic whole foods - with no more than 20-30 grams of carbs a day.  Sadly, its not showing that I'm in ketosis.  Trying to figure out if I need to wait more days until my ketosis becomes more pronounced or if real carbs vs net carbs is affecting my Ketonix reading.  
Any input would be welcomed.  


Have you tried testing your blood ketones? That would explain whether it's the device or you may not be in ketosis. Also, keep in mind that keto-adapted individuals show lower ketone levels:


I like my Ketonix. I'm a data nerd and blood strips are too expensive and urine strips too inaccurate. I occasionally test blood BHB after a reading to see how the numbers correlate. 46 was 1.1, 59 was 2.2, So the 40-70 nutritional ketosis range seems to be pretty accurate. (Mine has 3 range settings as someone said below). After I get to my goal weight, I plan to use it to see how many carbs I can eat and stay in ketosis.
I was looking for more info on breath acetone levels and weight loss. I thought this research was interesting. It shows that increasing fat from 79% to 90% reduces ketones. All the more reason to calculate macros and log intake.


Thank you for your insights. It's worth knowing that more fat doesn't always lead to a higher ketone level. I noticed that the ultra high-fat diet is a popular trend these days - often for people who don't even need to aim for high ketone levels. The reason why a 90% fat diet leads to a decreased ketone level could be what the suggested in the study: a lower ketone level could be caused by better utilisation of ketones and ketone production is decreased.
Here are a couple more interesting facts:
- exercise can decrease ketone levels because they are used immediately for energy (I suppose this mostly applies to keto-adapted individuals).
- the emphasis on personalised approach/nutrition (e.g. people with lower body fat have higher ketone levels and higher metabolic rate generally metabolise fat more effectively).


Good info.
I started using my Ketonix a few days ago after going onto a LCHF diet a couple of weeks ago, and though my 'diet' hasnt been perfect its been mostly on track. I havent snacked since I started LCHF and I only eat LCHF yet my results using this device have been in the 20's range which is obviously disappointing. Then today I read some more info on using this device which seemed to say I shouldnt be saving my data until the device has finished analyzing the sample (which was not clear in other documentation/advice I've read and is made the more confusing as I get a prompt to save before it starts analyzing AND after. So I did the test again and ignored the first prompt to 'save', let it analyze, then saved the data at the second prompt and my result is 55!


I am confused, if the ketone urine strips are inaccurate because of measuring acetoacetate, how is the Ketonix more accurate measuring the the acetone which is a break down of the acetoacetate?  Wouldn't that be also measuring the "wasted" ketones which would not be so prevalent when you are keto-adapted?  Thank you so much for you blog site.  Very helpful!


Hi Deborah, although acetone is a break down product of acetoacetate, it's not the same as the "wasted" ketones (acetoacetate) via urine. There is a correlation between the level of blood ketones and breath ketones but it's a bit more complicated (see the link to the in-depth review).


Thank you for this!  I had not been able to view my results until I read your post.  I have to say that the companies tutorials are not so informative.  Customer support did not clear things up so I am happy to have "googled" and found you!


Thank you Kate, I'm glad you found it useful!


I like my Ketonix. It does a good job of telling me my ketone levels, if only roughly. I prefer my BHB blood teat strips and also glucose strips to see my glucose ketone index ratio but that may be a temporary phase. Ive simply been having great success using a ketogenic/primal/paleo diet. Even more so with intermittent fasting and weekly 24-48 hour fasts. Whats more is i feel great doing this; better than i have in a long time.  Be healthy everyone and dont hurt yourself with food, neither with excess nor insufficient quantities. Remember gealthy fats and nutrient dense vegetables. Keep focus and be a friend to yourself.


With the new model, there are three available settings: Standard, Nutritional, and Sport. Can anyone explain the benefits of one over the other? We have the option of adjusting the sliders in each of the settings. How would we determine that's something we should do?


I haven't seen three settings - just two - so I suspect I don't have the latest one. I use the "Standard" one and I'm not sure what the difference is but I think it's just personal preference of where you want to have the limits.


Thank you for this! You answer some questions that I have been unable to find the information anywhere on the Ketonix site. I tried to contact their customer service and we just could never connect because of the time differences. This really clears up a lot, and I look forward to using my Ketonix more appropriately in the future. Thank you.


Thank you, I'm glad it helped! Smile


Thank you for this information! It is the only reason I could figure out how to set this darn thing up and take readings. GAH!!! So I left it at the settings it came with and have the blue model. Seems to work fine. I blow for 20 seconds to get all the air out. I will remain consistant. I use my phones stop watch. If I were to take on vacation and NOT have a battery can I still use it plugging into a wall socket? Just go by the color and number of times it flashes?
Do you find that drinking water affects the readings? I read this somewhere, so drinking a large glass of water making it read lower?
Thank you, again!!


Hi Lori, I haven't tried that but I think that should work provided you have the right connector. Yes, the idea is that if you use the battery, you go by the colour so it gives you a range. I don't know if drinking water affects readings on the Ketonix but I'd avoid drinking a large glass of water just before measuring.


I bought the ketostix as I am type 1 diabetic and athlete and after stabalizing my BG want to continue to be able to utalize the endurance and improve my performance. On your blog and on the website I can not find the conversion factor from the ketonix reading to the united states readings, also I know you can use the ketonix with a portable battery (so you can use it away from a computer and it can be portable, which I need) however I can not find any information if the device will store the data it collects when not attached to a computer. Are you able to answer these questions? Thanks so much!
Kind regards


Hi Daisy,  if you use it with the battery (without being connected to your computer), it won't store any data but I seem to remember they are planning to add this feature at some point. When it comes to the readings and conversions, you might want to ask on the Ketonix website / support. Hope this helps!


Hi Martina,
You mention that level of ketones will not tell you how much fat you are burning, check out the info in this study / review which can be found through a link from the Ketonix webpage which states higher level more fat burn. PS love the app


Thank you Paul! I will have a look and let you know once I go through the study.


Thanks for this information Martina. I have had one of these breathalysers and use it ad hoc but had no idea it came with software. I bought the unit via an Australian low carb website. Interesting information. I use it now and then to double check I am still in Ketosis but I must say I don't use it regularly.  Next year I will focus a bit harder on weight loss. This year my focus was to get my health issues under control and that goal I seem to have achieved and I am sure this WOE helped greatly.


That's great Inge, that's the right way to do it in my opinion. Well done and good luck with your new goal!


I use an old version and keep records manually, each morning (blue/green/orange/red).  The only time I go into blue is when I have a shop bought sugar/chocolate sweet the previous day (not often); or if I've eaten too much meat/protein.  My range used to be in the green regularly until I started taking spicy coconut oil fat bombs daily and now it varies between green and orange.  My mighty mitochondria is much happier when I follow a mostly vegetarian diet with fat of course, small amounts of protein and I also take kombucha and kefir daily.
I've struggled to loose weight on the keto lifestyle, but the health benefits outweigh that problem.   5 : 2 fasting for a few weeks at a time moves a couple of kilos, but I have to be in the mood for that !


That's great Georgina! I do intermittent fasting every now and then - it depends how I feel and if I don't feel hungry, I just skip a meal or two. So on most days, I have no breakfast.


Dear Martina,
Thank you for your clear explanation. After reading your blog I bought a Ketonix.
And your blog was really helpful with downloading the software.
I’m a Dutch dietician and psychologist and I coach people in their weight losing process.
Normally I use the ketostix and recently I bought a blood keton meter. For this meter it is very clear what the best values are for weight loss.
My question is if you know what the ideal values are for weight loss with the ketonix? Is it between 40-70 or higher?
I’m looking forward for your answer.
Best regards,


Hi Eveline, I don't think that there is any known value that is best for weight loss. I do see recommendations over the Internet every now and then but there is no scientific evidence for that claim.
The level of ketones itself has a very small effect on weight loss - in fact, the main reason people lose weight on a ketogenic diet is the appetite-supressing effect of low-carb diets. There are cases where people go "zero-carb" and they actually put on weight because they eat too much fat. High level of ketones may have therapeutic uses or may enhance performance in athletes but it does not necessarily enhance weight loss.
The "ideal" carb intake for weight loss may be 50 grams for some people and 20 grams for others. I'm not a health professional but I would not make any general recommendations for carb intake / ketone levels.


I bought the sport model and have yet to get a reading on it! I have been in ketosis but it does not blink any other color light! So can I use the website with my unit? I bought it quite a awhile back and didn't have any information on the website, will it work with the older model?


Hi Nita, I'm not sure how the old model works - I tested the new one. I think that if you want, they can send you a new model (in exchange and with additional payment) - I think you can get an upgrade. If you go to their "products" page, they offer this option so you might want to contact them.


Hi Nita, I have one of the old sport models too.  I find that I have to plug it in for a long time until it stops blinking - then it is ready for you to blow into.  I thought mine wasn't working for a while until I discovered this.


I love my breathalyzer! I was so tired of paying for the blood strips and this does exactly what I need so I know whether or not I am in ketosis. I use it twice a day and sometimes even more to see how certain foods affect my ketone levels. I just wish it was available on Amazon in the US...


That would be great. I think it used to be on Amazon.


I bought my 2015 model off of Amazon in the US - it works great, your blog post helped me with the calibration a bit... It's hard to get away from blowing a full lungs worth - what really matters is the last part of your breath and then being patient to let it analyze for up to 30 seconds and settle on the correct reading.  Althougth I bought the Ketonix Red (sport) - I have it configured via the software to operate as a standard model to start until I'm fully Keto adapted and into performance way of life needing to measure higher PPM.


Thank you so much for your review! I bought one about two weeks ago and although I figured out the software I was still having problems.
Result: thanks to your note, I found out the little holes weren't lined up and so the air was just being pushed in and I couldn't get to the bottom of my lungs.
Success! I finally have a reading and it was in the high 40's. Thank you again!


Awesome! I had the exact same issue first time I used it Smile


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