What factors affect the Keyto Level?

We have engineered a precision nanosensor that can detect acetone in human breath at a concentration of 1-2 parts per million (PPM). To put this in perspective, consider a box with a million grains of sand and consider finding the one red grain out of a million yellow ones. That is what the Keyto does! That said, the measurement of breath acetone can be affected by more than just the things you eat which lead to fat burning and ketone production. We thought it would be helpful to review some of the non-nutritional factors that can affect the reading of breath acetone.

Note – the most common cause of high readings is from alcohol. While the sensor is highly selective for acetone, the amount of alcohol in one’s breath after even one drink is 10-100x the amount of acetone. Thus, we recommend taking Keyto measurements before your first drink of the day. (Measurements taken within 8-12 hours of drinking alcohol may be contaminated).

There are 5 broad categories that can cause Keyto Level readings to fluctuate higher or lower but do not relate to how well you are adhering to the ketogenic diet:

  1. Physiology
  2. Breath characteristics
  3. Environment
  4. Contaminants
  5. Acetone Sensor


There is much we know and much we do not know about the physiology of ketogenesis. For the purposes of this discussion, we will focus less on ketone production and instead on the kinetics of clearance. That is, not how fast your liver makes ketones, but instead how fast your body clears them or uses them as fuel.

We know that many things can affect the balance between production and clearance. These include exercise (reduces immediately but increases longer term), sleep, stress, and body composition (how much lean muscle or fat mass your body has).

In addition, we also know that clearance can be affected by how insulin sensitive your body is. That is, how effective is insulin at doing what it is supposed to do (disposing of glucose)? In general, individuals with better insulin sensitivity will dispose of ketones more efficiently than those with lower insulin sensitivity. This can mean that if your insulin sensitivity is higher, you might end up with lower Keyto Levels. Other considerations include using ketones as fuel. As you become more adapted to being in nutritional ketosis, your body adjusts and will use ketones as fuel which means the rate of clearance can increase, leading to lower scores over time.

Breath characteristics

One of the most important determinants of your Keyto level is how you blow into the Keyto device. The most important principle is that in order to get the highest score, you need to get to the bottom of your breath. The reason for this is that breath reflects blood acetone concentrations but that relationship is most optimal with breath that comes directly from a part of your lungs that is in closest contact with your blood. This is called the alveolus and it is a tiny air sac. To measure concentrations in alveolar breath and to most accurately reflect blood levels one needs to get to the very end of breath. The factors that determine how to get to alveolar breath include breath strength (how hard you blow) and breath duration (how long you blow). To get the most alveolar breath, it is critical to get to the bottom of your breath. Anything that precludes getting to the bottom of breath will affect the accuracy of the score.  How you blow matters!


Many things in the environment can affect the accuracy of the measurement. The Keyto has a sophisticated precision nanosensor and it can be affected by both temperature and humidity. Variations in the performance of the sensor can be expected in extreme temperatures or extremes of humidity (high or low).


Besides breath quality, the most common cause of inaccurate readings are from contamination, which can come from the breath or the environment. Common sources of breath contaminants that can affect the accuracy of the device include mints, mouthwash, toothpaste, alcohol, tobacco, and other substances that contain volatile organic compounds that react with the sensor. Common environmental contaminants include perfume, rubbing alcohol, nail polish remover (acetone), kitchen cleaning liquids, lotions, and other solvents. In general, it is best to avoid using your Keyto around any of these.

Acetone Sensor

The creation of every Keyto Breath Sensor requires intense human craftsmanship as well as automated processes from sophisticated machines. Each sensor requires several cycles of assembly, validation, heating, cooling, and calibration. To ensure you have the best experience, every device is tested personally by someone on the Keyto team (most likely Ethan or Ray!).

Due to the complex manufacturing process, each sensor is slightly different. The small inter-sensor variability can result in differences in sensitivity to contaminants and environment, and can be magnified when we are measuring 2 parts per million of acetone.

The sensor may also require a couple of uses to stabilize as it learns your breath (and you learn how to blow optimally). Use it consistently for a week and you’ll be sure to get an accurate sense of your breath acetone levels.


We have done our best to engineer the most accurate and easiest to use acetone breath sensor possible. However, remember that  we are measuring acetone concentrations of just a few parts per million! As can be expected, there are many factors that can affect the results. Most of these are known and are easy to avoid, but some are also unknown. So if you get a result that does not make sense, start by considering the known factors described above. If it still does not make sense, take a break and try again the next morning.


For more context, here is a link to an image of one million dots. The Keyto is detecting just a couple of dots out of the entire batch!