If you’ve been following a low-carb or keto diet for a while, you probably know what you can and cannot eat to stay in ketosis. So there’s usually no need to take frequent ketone measurements or to stress out about the fact that your ketone levels naturally fluctuate throughout the day.
But if you’re like me and enjoy testing different foods or making lifestyle changes to see how they might impact your metabolism, then being able to accurately test your ketone levels in a non-invasive way is a plus.
In this article, I’ll give you an overview of four methods for measuring your ketone levels and explain why Biosense, a medical-grade breath ketone analyzer that’s been tested for accuracy in clinical trials, is the most accurate way for consumers to measure their ketone bodies.
I’ve been using Biosense for several weeks and I’m thrilled to share my findings.
Biosense Breath Ketone Monitor
Biosense is a breath ketone meter developed in the United States by Readout Health that boasts clinically-validated accuracy.
Biosense has been a gamer-changer in real-time ketone testing for me because I can use the device several times a day without incurring additional costs beyond the initial purchase.
Before we get into the specifics of Biosense, let’s briefly talk about the basics.
As I’m sure you already know, the main goal of a ketogenic diet is to get into and remain in nutritional ketosis, a metabolic state that allows your body to use fat instead of glucose (from dietary carbohydrates) as its primary fuel source.
While many cells in the body can burn fat directly, others (including brain cells) can’t. Instead, they require the liver to convert those free fatty acids into ketone bodies before they can use them for energy.
Types of Ketone Bodies
What you might not know is that there are three different types of ketone bodies, including:
- Acetoacetate (AcAc),
- 3-beta-hydroxybutyrate (BHB or 3HB), and
- Acetone (ACE).
Acetoacetate is an unstable ketone body that’s produced by the mitochondria of liver cells. After the liver releases AcAc into the bloodstream, it becomes the preferred energy source for the heart, renal cortex and brain. Since your kidneys excrete excess acetoacetate via the kidneys, you can measure this ketone body using urine test strips.
Acetoacetate is the first ketone your body produces and the base of both BHB and acetone. About 20% of the ketone bodies in your bloodstream are acetoacetate.
Beta-hydroxybutyrate or BHB is arguably the most well-known ketone body among followers of a ketogenic diet because it’s also available as a supplement (as exogenous ketones) and you can easily measure it using a blood or finger-prick test. BHB is also the most abundant ketone body as it makes up about 78% of all ketones in your system.
Technically, BHB is a carrier or storage mechanism that delivers energy from the liver (where it’s synthesized from fatty acids) to peripheral tissue. Some people think that BHB is the intended end-product of ketogenesis (the creation of ketones). However, it’s worth noting that BHB can’t be used for energy without being converted back into acetoacetate.
Acetone is the least abundant ketone. It makes up about 2% of all ketone bodies, and it’s not used for energy. Instead, your body usually excretes it quickly through sweat or your breath. The latter is why you can measure it using a breath ketone analyzer.
Much like BHB, your body makes breath acetone from acetoacetate, which is why you can correlate levels of ACE and BHB.
If you want to learn more about the different types of ketones, check out this article, which explains the key concepts in plain language.
Four Ways to Measure Ketones
Now that you know about the different types of ketone bodies, let’s talk about the four different ways of measuring them, including:
- Urine strips
- Capillary blood test (finger-prick test)
- Breath test (*using a medical-grade device)
- Venous blood test
The list above is ranked based on the accuracy of the testing method. Note that there are different types of breath ketone meters on the market and most of them are much less accurate than the clinically-tested device I’ll introduce you to later.
Urine Ketone Test Strips
Like most people who have just started their ketogenic journey, I used to use urine test strips to check if I was in ketosis.
However, there are several problems associated with urine test strips, including:
- They give you a semi-quantitative measurement of acetoacetate and they don’t detect BHB. In other words, they can only give you an indication of whether or not you’re in ketosis.
- The results often don’t equate to plasma (blood) ketone concentrations.
Additionally, as your body becomes more fat-adapted and proficient at using ketones for energy, it will excrete fewer of those molecules via the urine. As a result, you’ll likely run into the issue of false negatives after having been on a ketogenic diet for a while.
When I use urine test strips these days, I mostly get negative results because my body no longer excretes a high volume of ketones via urine.
My recommendation is to consider leveraging urine test strips only if your budget doesn’t allow for a more accurate ketone meter.
Capillary Blood Ketone Meters
Arguably the most popular way of measuring ketone levels is a capillary blood ketone meter, such as the one from Keto-Mojo* that I’ve been using for over a year.
The advantage of consumer-grade blood ketone testers is that they’re reasonably accurate and relatively easy to use.
The disadvantage of those devices is that you have to stick a needle into your fingertip, squeeze out a drop of blood and transfer that to a relatively expensive testing strip.
If you only want to test your blood ketone levels every couple of days, then neither the fact that you have to prick your finger nor the 80-cent-per-strip cost are issues.
But if you want to perform several tests per day, a traditional blood ketone meter can quickly become an expensive inconvenience.
For example, individuals who have diabetes (and who are at higher risk of developing ketoacidosis) have to test their blood glucose (and sometimes, their blood ketone levels) several times a day, unless they have access to a continuous glucose monitor and a simple breath ketone analyzer.
As far as accuracy is concerned, blood ketone meters are probably accurate enough for the average consumer who wants to confirm the effectiveness of their low-carb dieting efforts.
However, a systematic review of the accuracy of capillary hydroxybutyrate measurements devices concluded that:
Despite the advantages of the use of Point of Care meters for measuring capillary β-OHB, there are limitations. According to Dhatariya , there is evidence of poor performance of Point of Care meters at high levels of ketone concentration. This position is supported by Yu et al.  who demonstrated that the use of Abbott meter for the measurement of β-OHB correlates well with the reference laboratory method (Stanbio Assay) up to 3 mmol/L, and becomes discrepant after that value. The authors further observed that while the Abbott meter may be useful for the diagnosis of DKA, it may present challenges to clinicians in the management of patients with DKA who have β-OHB values greater than 5 mmol/L (reference method) in hospital settings.
Another study from Denmark confirmed that capillary blood tests may overestimate ketosis.
Taking into account the potential accuracy issues, cost and inconvenience, I prefer breath ketone meters over pricking my finger.
Breath Ketone Analyzers
Breath ketone monitors measure the amount of acetone in your breath. In other words, they can’t directly measure BHB — the ketone your body uses for fuel.
The problem with most ketone breath analyzers* is their reliability, as there are several factors that can negatively influence their accuracy or cause them to fail, including the use of breath mints, chewing gum, tobacco and toothpaste.
Additionally, the consumption of certain foods or beverages — such as alcohol, coffee, garlic and green tea — can negatively influence the test results.
If that wasn’t enough, your breathing pattern can also influence the test results, and you might have to periodically recalibrate the device.
Last but not least, when you blow into a breath meter, ambient air reaches the sensor and “dilutes” the breath sample. That can also lead to inaccurate test results.
These are some of the factors that made me stick with blood ketone testers until I stumbled across Biosense, a clinically-validated breath ketone analyzer that’s incredibly accurate and easy to use (see below).
Venous Ketone Blood Test
Having a lab draw blood and test your ketone levels is the gold standard of ketone testing. Unfortunately, it isn’t something you can easily replicate at home. But even if you could, it’s relatively invasive and not worth the trouble (unless you’re participating in a clinical trial, where 100% accuracy is crucial).
The reason why I mention this method is that you often hear that blood ketone testing is the gold standard. While that’s true, it’s important to make the distinction between venous and capillary ketone blood testing; the former is the gold standard, not the finger-prick test.
Biosense Breath Ketone Analyzer
Biosense is a breath ketone meter developed in the United States by Readout Health that boasts clinically-validated accuracy.
Biosense has been a game-changer in real-time ketone testing for me because I can use the device several times a day without incurring additional costs beyond the initial purchase.
- Clinical-grade accuracy
- Cost-efficient in the long-run
- Requires minimal maintenance
- Limited integration with other platforms
- Initial purchase price
How Biosense Works
Much like other breath ketone meters, Biosense measures the amount of acetone in your breath. But the way Biosense analyzes your breath is different from other devices.
For example, Biosense discards most of the air you blow into the meter (by redirecting the airflow away from the sensor) via vents on each side of the mouthpiece.
Biosense only starts collecting a breath sample for analysis as you reach the end of your exhale, which ensures that the device only analyzes the part of your breath that originated deep down from your lungs.
Biosense calls that technology deep lung sampling and claims it provides more accurate and reproducible results “by correcting for natural variations in exhalation time and lung capacity across individuals.”
Biosense is so good at deep lung sampling that it can even pick up acetone in the breath of our five-year-old. That’s quite a feat because the lung volume of kids is much smaller than that of adults. That’s why most breath analyzers don’t work for kids.
How does Biosense know when you reach the end of your breath? It uses a microphone that’s built into the meter to detect changes in the sound you make as you exhale. Pretty clever!
Discrepancies between Biosense and Keto-Mojo
The Biosense meter measures the amount of acetone in your breath, which you can easily correlate to blood ketone levels (BHB).
For example, if Biosense reports 16 ACEs, then your blood ketone level is approximately 1.6 mmol/L. Published studies and Biosense’s own clinical trials have confirmed that there is an approximate 10-to-1 correlation between acetone and BHB. Biosense told me that this 10-to-1 correlation is by design to make it easier for clinicians to understand the ACEs value.
When I first got Biosense, I couldn’t help but compare the results with the results from my Keto-Mojo meter. While the readings of both devices correlated in some of the cases, more often than not, Keto-Mojo showed higher ketone readings than Biosense.
After some digging, I learned that most capillary blood ketone meters overestimate ketosis, as confirmed by this Danish study that compared capillary and venous blood ketone tests.
The authors of the study confirmed that while capillary ketone blood meters are relatively accurate at detecting relative changes in blood ketone levels, they often overestimate the absolute amount of BHB in the blood.
So keep that in mind if you decide to compare Biosense with your existing blood ketone measuring system.
Biosense comes with a rechargeable battery that lasts a couple of days, depending on how often you use the device.
The charging time is approximately two hours via micro-USB.
Biosense doesn’t require a lot of ongoing maintenance, but you should clean the mouthpiece every so often because it’ll likely accumulate saliva from your breath.
Speaking of the mouthpiece: Biosense includes two replacements in the box. Since the tip of the mouthpiece is medical-grade nylon, it shouldn’t wear out anytime soon. But if it does, you’ll be covered.
The Biosense breath ketone monitoring system includes the Bluetooth-enabled meter, a Micro-USB charging cable, two replacement mouthpieces, a protective neoprene sleeve and a mobile app.
The price for the complete system is $299. While that sounds like a steep price for a ketone monitor, keep in mind that you can test your ketone levels an unlimited number of times. In other words, you won’t have to keep buying test strips or periodically recalibrate the device.
If you have a flexible spending account (FSA), you even can use that to get reimbursed for the cost of Biosense.
Note that you can use discount code Kummer20 at checkout for a $20 discount!
My Experience with Biosense
My experience with Biosense has been mostly positive, even though it didn’t always report the ketone readings I wanted and hoped for.
For example, after our vacation to Mexico — where I consumed slightly more carbs than I usually do — it took me several days to get back into deep ketosis. I thought that my body would be quicker at switching back to burning fat for fuel. So I got frustrated when I saw readings in the range of 3-5 ACEs for a few days.
Obviously, that wasn’t the device’s fault. But it was annoying nonetheless.
Biosense wasn’t made to be shared or used with kids, but that hasn’t prevented me from letting my wife and kids use it as well.
To my surprise, Biosense worked incredibly well with both our seven-year-old daughter and our five-year-old son. In fact, those two have consistently scored better breath ketone readings than my wife and me.
Lucas, our youngest, clocked in at 36 ACEs one morning after skipping dinner the night before. Needless to say, we didn’t make him fast; he decided to play with his toys rather than eat.
The lesson I learned from those experiments was that intermittent fasting is the quickest way to get into ketosis, and that the smaller glycogen stores of kids make it much easier for them to get into and stay in ketosis.
Our kids usually eat more carbs (in the form of fruits and veggies) than we do, yet an overnight fast (while sleeping) catapults them into deep ketosis while we remain at moderate to advanced breath ketone levels.
Another lesson I’ve learned is that eating too much protein can trigger an insulin response that can impact my ketone readings without also impacting my blood glucose levels.
You can check out this video I published on YouTube to learn more about that experiment.
I performed that experiment just for fun and out of curiosity, but if you have diabetes or another disease related to insulin, you could use Biosense to test how your body responds to certain foods by releasing insulin.
What I Would Improve
I’ve grown very fond of the Levels Health app*, part of the continuous blood glucose monitoring system I use. It automatically correlates food intake and physical activity with changes in blood glucose level.
I’d love for Biosense to offer similar capabilities via its mobile app and offer direct integrations with some of the other platforms I use, including Apple Health, Eight Sleep, Levels Health* and WHOOP.
That would make it much easier for me to correlate food intake, strenuous physical activity and sleep performance with changes in my ketone levels.
The good news is that Biosense already integrates with Cronometer, Heads Up Health, Senza, LifeApps and additional integrations are in the works!
Frequently Asked Questions
Biosense is intended to be used by a single person. Nevertheless, I’ve been sharing Biosense with my wife and kids on occasion. The downside of doing that is that their test results show up in my mobile app and I have to manually delete them to keep track of my own readings.
As I mentioned above, Biosense hasn’t been validated for use with kids. I’ve been using my Biosense with our kids anyway and it’s been producing good results as far as I can tell.
The acetone levels in your lungs don’t change very quickly. So there is no benefit to performing back-to-back tests. Additionally, it takes about five minutes for the acetone molecules in the device to dissipate after a test. That’s why Biosense recommends waiting at least five minutes between tests.
Yes, clinical trials have confirmed the accuracy of Biosense and the correlation between breath ketone (acetone) and blood ketone (BHB) levels.
A venous blood test is the gold standard of ketone testing. But unless you’re working in a clinical setting, you will likely not have access to such tests. For consumers, clinically-validated breath ketone monitors like Biosense are the next best option, followed by capillary ketone blood tests.
Ketone bodies can be used for fuel almost exclusively by aerobic cells like heart, muscle, brain and kidney cells. However, red blood and liver cells can’t burn ketones for fuel and require glucose.
Besides reducing your carb intake to under 20 grams of net carbs per day, the fastest way to get into ketosis is intermittent fasting, followed by the consumption of medium-chain triglycerides (e.g., MCT oil powder*).
Depending on the number of uses per day, the sensor should last one to three years (or longer). The company will also launch a recalibration and sensor replacement service soon, which will cost $75.
Wrap-Up: Biosense Is the Best Ketone Analyzer on the Market
If you’re serious about keeping tabs on your ketone levels in the most convenient, cost-effective and non-invasive way, Biosense is the best ketone meter you can get*.
As I mentioned above, I’m not a fan of “chasing ketones” because it’s unnecessary once you have your dietary lifestyle dialed in.
But if you want to experiment with different foods, exercise and other lifestyle factors in order to learn how those changes might influence your body’s ability to burn fat for energy, having access to a reliable breath ketone analyzer is an advantage.
I’ve been using Biosense for the past several weeks and I don’t see myself going back to finger-prick tests.
Now I’d like to hear from you! Where are you on your ketogenic journey and how have you been measuring ketone levels? Let me know by leaving a comment below.
I’m a healthy living and technology enthusiast.
On this blog, I share in-depth product reviews, actionable information and solutions to complex problems in plain and easy-to-understand language.