Review: BIOSENSE keto monitoring

Deep lung monitoring for keto makes good Biosense.

Having followed a ketogenic diet for two years, to improve chronic migraine, and knowing multiple individuals that utilise the ketogenic diet for prolonged energy release in endurance sports, I was incredibly excited to trial out the new, only clinically backed, breath ketone monitoring system BIOSENSE.

The BIOSENSE ketone monitor has been designed by Readout, Inc, a digital biomarker company that works with pharma, academic research and clinical partners to advance the use of nutritional interventions in chronic disease management.

In my own words, the BIOSENSE is a hand-held, highly accurate, convenient device that quickly gives you a readout of your ketone levels simply by blowing into the mouthpiece for 3-5 seconds. Your ketone reading is then presented to you as ACEs, a unique unit of breath acetone provided by BIOSENSE.

GO LONG    GO SHORT
  • Not invasive and convenient
  • Battery life  
  • High accuracy of overall daily ketosis levels
  • Initial purchase price
  • FDA registered device
  • Very loud vibrations when switching the device on
SCORE: 4/5 ***** User interface and user experience: How positive or negative is the experience when using the product and associated apps, login pages, product support and associated services?
SCORE: 4/5 **** How does it stack-up with competitors or similar products or services?
SCORE: 4/5 **** How well has the company conducted or utilised scientific research and studies to validate its product/service?
SCORE: 3/5 *** How applicable is it to the Longevity marketplace and the daily life of a Longevity enthusiast?
SCORE: 4/5 **** How easy it is for a layperson to use the product/service and its associated benefits in the context of Longevity?

We scored BIOSENSE at 22/25, here’s the low-down:

Nutritional Ketosis and Healthspan

Nutritional ketosis can be reached by following a ketogenic diet (high in fat, low carb and adequate protein) or through intermittent fasting. Both scenarios deplete the body’s glucose reserves, resulting in endogenous ketone bodies being produced through liver fatty acid metabolism to serve as an alternative energy source for important organs like the brain and the heart [1].

There are three different types of ketone bodies: acetoacetate (AcAc), 3-beta-hydroxybutyrate (BHB) and acetone (ACE). All three circulate in the blood stream but only acetone can diffuse into the lung and be exhaled due to its small size.

Clinicians and researchers have deliberately induced the state of ketosis to treat a variety of pathological conditions including severe epilepsy, type-2 diabetes, metabolic syndrome, obesity, polycystic-ovary syndrome, acne, cancer, migraines, and other neurological conditions [2]. However, the mechanisms behind the benefits of ketosis for these conditions are not yet well understood.

We know that there are different factors that will impact how different individuals react to a fixed dietary protocol; metabolic rate, glycogen stores in the liver and other factors in ketone production will change dependent on the individual and produce different rates of ketosis.


Having an easy way to track your ketone levels, from the comfort of your sofa, can provide you with important insights into what levels of nutritional ketosis you need to hit throughout the day to maintain a therapeutic value.


Although not directly related to enhancing lifespan, nutritional ketosis could maximise quality-adjusted life years for those suffering from a variety of pathological conditions. Having an easy way to track your ketone levels, from the comfort of your sofa, can provide you with important insights into what levels of nutritional ketosis you need to hit throughout the day to maintain a therapeutic value.

Fasting and longevity

Furthermore, fasting, refraining from food and beverage, for 12-24 hours, triggers a metabolic mode in which fat-derived ketone bodies and free fatty acids are used as main energy sources. Fasting has impacted longevity various animal models in various lab studies, albeit to different extents.

If fasting is something that you want to try for cellular protection, aging and regeneration, how long your body takes to flip into ketosis during your fast may differ from the general recommendations. The BIOSENSE device will provide you with a good indication as to what stage you are in your fast by providing a read-out of ketone levels.

The science behind BIOSENSE

BIOSENSE uses deep lung sampling to measure the levels of ACE in your breath. This means that only the last part of your exhalation, which contains the most volatile compounds such as acetone, is collected. The device detects the breath when you first blow into it but does not activate until it senses the end of your breath.

After the device measures the acetone in your breath, in parts per million (ppm), it is converts it into ACEs, a unique unit of breath acetone developed by Readout, Inc. The conversion from ppm to ACEs is proprietary, but essentially the developers at Readout have used both historical data and their own internal data to map ppm onto a blood ketone equivalent.

The ACEs unit is designed to be approximately ten times the blood BHB equivalent. In other words, if you have 1.0mM of BHB in the blood, you expect to be around 10 ACEs on BIOSENSE.

A BIOSENSE customer using the device. Source: BIOSENSE

So how accurate is the device? A 14-day prospective observational cohort study followed 21 individuals consuming a low carb/keto or standard diet. These individuals recorded their ketone levels 5 times a day using both blood (BHB levels using blood monitors) and breath (acetone levels using BIOSENSE) ketone monitoring methods. There were three interesting points that resulted from this study [3]:

  1. Both the levels of BHB in the blood and acetone levels in the breath had high variability throughout the day. This is probably down to diet and exercise, but this is a positive finding in terms of the device; because both the blood BHB levels and breath acetone levels varied, you can be confident this variability throughout the day is due to physiological ketone changes in the blood and not due to the changes in breathing pattern. Put simply, this implies that one single daily measurement of ketone levels is not sufficient to show your daily ketone exposure and multiple measurements throughout the day will give a better idea of your overall daily ketone dynamics.
  2. The study used receiver operating characteristics (ROC) analysis to determine whether the BIOSENSE monitor had the ability to predict the levels of blood BHB. The ROC analysis demonstrated that the BIOSENSE device was a good/excellent classifier of blood ketone level states for certain thresholds.
  3. However, for some individuals, the study also showed that there was an indirect physiological relationship between breath acetone levels and blood BHB. Whilst they typically changed at similar rates, the concentration was often offset in time; the concentrations of blood BHB peaked approximately 4 hours before breath acetone peaked. Readout believes this is due to the indirect physiological relationship between breath acetone and blood BHB resulting in an unpredictable relationship between changes in breath acetone and changes in blood BHB. Further studies are needed to fully characterise these changes.

The takeaway from this study was that, as ketone levels can vary greatly throughout the day, a single ketone measurement is not sufficient to provide an overview of an individual’s metabolic state. For most clinical applications of ketosis, you want to know the cumulative picture of the body’s exposure to ketones. To account for this, and the offset in time between breath and blood ketone levels, the BIOSENSE app provides an accumulative daily ketone score calculated using “area under the curve” from the ketone measurements taken over the space of a day by the user.

The area under the curve is basically a summary of the depth of daily nutritional ketosis reached by the individual and answers the question “how deeply and for how long have I been in ketosis?” with a single number. The predictive power of the daily AUC (called “ketone score” in the app) is very good and ketone exposures for blood and breath are highly correlated (>0.8 correlation)6.

My experience with BIOSENSE

I have enjoyed gaining insights into how my body reacts to carbohydrates and ketosis. I started by reducing my carbs intake to 50g a day, the recommendation to be able to flip the body into “fat-burning keto mode”. It took me nearly 2 days before, according to my BIOSENSE, I hit moderate ketosis levels (5-14 ACEs).

Frustratingly, my ketone levels plateaued at 5-8 ACEs for about a week. I experimented and took my carbohydrates levels down further to around 25g of carbohydrates a day. A day later and I started to reach “advanced ketosis” levels (15-30 ACEs). This is a dietary change I would have never attempted if it were not for my BIOSENSE monitor and I now have the insight that to reach higher levels of ketosis my body requires less than 25g carbohydrates a day.

Furthermore, the BIOSENSE app lets you add in food, exercise, fasting, weight and notes under each day so you can see the impact of certain activities and food types on your overall levels of ketosis. I used the food section to track what meals and foods had the most impact on my ACE score. For me, raspberries, and blueberries (allowed in small amounts on a ketone diet) continuously made my ketone levels drop toward “low ketones” (ACE 4) around 2/3 hours after consumption.

If I ran for over 30 minutes my ketone levels were higher after the exercise than the rest of my ketone levels throughout the day. Both insights make sense; raspberries and blueberries are higher in sugar than nearly everything else I was eating, and prolonged exercise will cause my body to burn more fat when my blood glucose levels are already depleted. But seeing these changes using the BIOSENSE app was remarkable.

A BIOSENSE customer using the device. Source: BIOSENSE

I also did a spot check just to make sure that the device was really working: my flatmate consumed a slice of chocolate cake and an hour later we took her ketone measurements using BIOSENSE.  Even though the device had been measuring moderate ketone levels from me throughout the day, unsurprisingly, the device came back at an ACE score of 0 (although she did add the cake was worth it).

There are just a few tweaks I would make… Firstly, the vibrations when you turn the device on are not discreet; if you are going to take your ketone levels in public do not place your BIOSENSE device down on a table, after you switch it on, if you would like to avoid a few awkward stares. Secondly, I wish the app would sync automatically to diet apps and exercise trackers, like MyFitnessPal and Strava.

Thirdly, I found the battery levels on my device reduced quickly and I was charging it nearly every day. However, these are small moans for a device which saves you from peeing on a stick or drawing blood to measure your ketosis state. At the moment the device only provides information suggesting that an “overall ketosis score of 120 is necessary for fat burn”. As this device is used in more and more clinical studies, it will be interesting to see if this information is updated to give insights into the ketosis score required for different pathologies.

If you want to gain insights into your levels of ketosis, BIOSENSE is my go to recommendation. Although a costly one-time purchase, the insights are worth it if you are attempting a first-time ketone diet or if you are a keto enthusiast.

Read our interview with BIOSENSE CEO Jim Howard here.

[1] https://www.dietdoctor.com/low-carb/ketosis
[2] https://www.nature.com/articles/ejcn2013116
[3] https://peerj.com/articles/9969/

Images courtesy of BIOSENSE

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