The Best Way To Test For Ketosis & Track Your Blood Glucose.


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In past articles…

…including “The Ultimate Guide To Biohacking Your Blood Sugar Levels (And Why Sugar Sometimes Isn’t Bad).” and “5 Simple Steps You Can Take To Live Longer, Banish Blood Sugar Swings & Massively Enhance Energy Levels.” …

…I’ve highlighted the extreme importance of monitoring or somehow self-quantifying your blood glucose levels.

And in my article “How To Get Into Ketosis“, I discuss the importance of ketones and ketosis and how to get into a state of ketosis efficiently.

However, today, I’d like to discuss how to actually test whether or not your efforts to manage blood glucose or increase ketones are actually working!

How to Test Your Blood Glucose

While a single blood test using an inexpensive blood glucose meter like this from any drugstore or health website can give you a static, single snapshot of your blood glucose levels, nothing beats a continuous blood glucose monitor for truly determining how your diet is affecting one of the most important parameters of your health and fitness: glycemic variability.

A continuous glucose monitoring system (CGM) is a system that does just what it sounds like: it monitors your blood sugar continuously, 24 hours a day. The data is transmitted from a sensor which is inserted right beneath your skin, and this is attached to a transmitter which sends the data to the receiver. You are then able to see your blood sugar at any point via a receiver or a phone app.

For those of you who want to know the results of my own 24-7 blood glucose monitoring using my Dexcom G6, which is currently implanted on my right abdomen, you’ll just have to wait, as I’m working on a report of the results. In the meantime, here’s a fascinating read on what you can actually see when you monitor your blood glucose with a continuous blood glucose monitor.

The basic way any CGM system works is via a tiny sensor inserted under the skin of your abdomen or on the back or your arm that is typically worn for 7-14 days (in my opinion, if you are eating your normal diet, you eat the same things regularly, and you test for two weeks, you’ll know everything you need to know about your blood glucose and can likely stop testing at that point unless you’re wearing the CGM for medical reasons). This sensor will be reading glucose levels in the interstitial fluid below your skin’s surface and is attached to a transmitter which sends the glucose level data wirelessly to an insulin pump (if a diabetic is using the CGM) or other receiver or smartphone app.

This means that at any given time during the day or night, you can look at your device and see how your blood glucose level is trending, and even receive instant notifications if it gets too high or too low. Since CGM is measured over a range of time, such as over minutes or hours, one of the best values to pay attention to are your postprandial (post-meal) blood glucose levels. The ideal postprandial levels range from 78 mg/dl over two hours following the meal (in men) and 81 mg/dl over two hours following the meal (in women). A healthy fasting blood sugar that is normal for people without diabetes ranges from 70–99 mg/dl, although I personally try to keep my sugar below 80. Within two hours after a meal such as a large breakfast, lunch or dinner, levels should ideally be less than 140 mg/dl.

The two most popular CGMs – both of which I’ve experimented with and found to work well, especially when covered in kinesiotape or some kind of ace bandage for high-intensity workouts, races, swimming or sauna exposure – are the Dexcom Continuous Glucose Monitoring System and the Freestyle Libre. Admittedly, because of my highly active lifestyle, I was nervous about using a continuous blood glucose monitor due to my fears that it would constantly become detached from my body, become water damaged, or that the extremely small needle that is inserted between the CGM and the skin would become bent. But as long as I am careful to tape the CGM prior to intense physical activity, it seems to stay attached and continue to take good readings, especially the more expensive but far more accurate Dexcom G6 model. The SIMPATCH adhesive patch for Dexcom works particularly well for this.

Now don’t get me wrong: owning a basic, cheapo blood glucose meter is a good idea, but if you can convince your physician to write you a prescription for a CGM (here’s one guy’s sneaky way to do it with an insulin overdose, which I do not recommend), it is well worth the insight you get. I personally didn’t get insurance for my Dexcom and had to pay a few thousand dollars for an entire year of tracking, but the expense is worth it to me, because I’m getting a lifetime’s worth of valuable data I can act upon to enable myself and many others to become healthier (yes, I invest in things like this instead of nice cars and fine China).

How To Test For Ketosis

In addition to blood glucose, it can be very insightful to measure your ketone levels, which are reflective of how efficiently you are burning fat, or how efficiently you are producing energy, even in the absence of high blood glucose levels.

Assuming you do not possess genes that would make you respond deleteriously to a high-fat, low-carb diet, ketosis can be a powerful nutrition approach to use switch your metabolism to prioritizing the use of fat as a fuel, while also increasing cognitive and physical performance (incidentally, even if you’re not achieving ketosis via a high-fat, low-carb diet, you can still amp up ketone production by intermittent fasting or engaging in other forms of calorie or carbohydrate restriction). Many people just assume that if they are “low carb” or fasting they are in ketosis, but it can be useful, especially if you’re just getting used to a new diet or supplement and trying to determine whether or not it increases ketone production. Ideal blood levels of ketones to indicate if you are in a state of ketosis range from at least 0.5 millimolar up 3.0 millimolar.

There are actually three testing methods for ketosis because there are three forms of ketones in your body: acetoacetate, acetate and beta-hydroxybutyrate, which can be tested in your urine, breath or blood, respectively.

Let’s begin with acetoacetate. The way ketones get into your urine is if they are “spilling over” in excessive amounts. This means that if there is an excess of ketones or if you are not actually utilizing your ketones efficiently, they can be dumped into your kidneys to be excreted in your urine as acetoacetate. The way to measure these excess amounts of ketones is through a urine strip, which changes colors relative to the number of ketones in your urine (usually the darker purple color on the strip, the more ketone bodies).

Unfortunately, this is not always a reliable test. Once your body is in a “keto-adapted” state and you’re burning ketones (including acetoacetate), you will see a progressively lower level of ketones that are reading on the strip. This is misleading since you may actually be in a deep state of ketosis but the strip says you have low ketones. In reality, there are just fewer ketones spilling over into your urine. So urine strips can be a cheap and effective testing method if you are just starting to get into ketosis, but aren’t a viable long-term or consistent test once you’ve been consistently in ketosis.

Acetone (also called acetate) is the second ketone body and is produced by gas exchange in your lungs. Acetone has been found in research to correlate very closely to levels of BHB in the blood and can be measured directly through the breath with use of a breath-measuring device.

One of the key advantages of a breath meter for testing ketones is that it is reusable and usually involves a one time purchase of a breath-measuring device such as a Ketonix, a Keyto or a LEVL.

Finally, the primary ketone body that you use for energy (or can take as an exogenous ketone supplement) is beta-hydroxybutyrate, or BHB. BHB enters the cell and is converted to acetylacetone, which can then be ultimately converted to acetyl COA and enter the Kreb’s cycle for production of ATP. A blood test for BHB can be done easily at home the same way individuals with diabetes check their blood glucose. You simply prick your finger, squeeze a drop of blood out of your finger, tap it on a strip and a small handheld reader will tell you the level of BHB in your blood. This is the most direct and accurate way to measure your level of ketosis. The downside to the blood ketone meters is that some people may have a strong aversion to needles and blood, and the testing strips are considerably expensive, usually $5-$10 per strip (although a newer device called “Keto Mojo” has dropped the price of ketone strips down to 99 cents per test). The blood level of BHB is measured in millimolar concentration, known as mmol. Studies have shown most optimal ranges of BHB levels for benefits of ketosis are between 0.5-3.0 mmol, although this varies based on activity levels, time in ketosis, fat-burning efficiency, etc.

So how do I personally test ketones? Although, as mentioned above, I wear a CGM (the Dexcom G6) to monitor my blood glucose, I’m not a fan of the hassle or expense of constantly measuring blood ketones. Instead, I use the device mentioned above, a LEVL, to monitor my breath ketones.

Here’s how it works…

…during ketosis, the body generates molecules called ketones, one of which, as described above, is acetone. Because of its small size, acetone can appear in your exhaled breath as an indicator of fat burning and can be relatively (although not precisely) accurate representation of your blood ketone values.

Clinical research has demonstrated a correlation between the amount of acetone detected in the breath, blood ketone values and body fat burned, giving a reliable indicator of ketosis fat loss. A breath ketone measuring device such as the LEVL is designed to detect trace amounts of acetone in your breath when your body is burning fat. You simply breathe into it, and your breath is captured then analyzed by LEVL’s nanosensor, providing you with an instant measurement of your body’s acetone concentration.

When you first shift into a lower carbohydrate intake, your body increases the amount of fat it uses for energy relative to the amount of carbohydrates, and your breath acetone concentration ramps up. This increase happens over the course of 3-7 days until you reach an elevated level of breath acetone. If your diet becomes high in calories or high in carbohydrates, your body will become less dependent on fat for energy. This will result in an acetone concentration reduction over the course of 1-2 days.

I prefer this method of breath measuring since it’s quick, easy and gives me a quick glance at my approximate level of ketosis. It does not measure blood mmol concentrations, but I still find it far easier and more convenient than blood testing for ketones. If I were to test blood, I’d prefer to use the KetoMojo, which is the most affordable solution.


That’s it!

In summary, while an inexpensive blood glucose meter can do the trick for blood glucose monitoring, a CGM is a far better solution for actionable insight without the hassle of pricking your finger.

And for ketones, I prefer breath measurements, for the reasons stated above.

Do you have questions, thoughts or feedback for me about testing glucose or ketones? Leave your comments below and I will reply!