Eating a ketogenic diet, practicing intermittent fasting, and experimenting with exogenous ketone supplements and MCT products are all ways to promote ketosis.
Ketosis can have several benefits for health, performance, and longevity. This is because ketones, the molecules responsible for ketosis, can serve as sources of fuel in the brain and body, even performing other signaling functions. The question is, how do you know if your lifestyle is actually getting you into ketosis?
The only true way is to actually test for ketones.
Similar to someone measuring blood glucose, testing for ketones can be done almost anywhere. It’s relatively simple and, depending on the method—not too expensive. Furthermore, testing for ketones can be a great way to get instant feedback on your diet and lifestyle habits.
Why You Should Test for Ketones
There are many ways to track progress towards a goal.
If you’re on a diet, this may involve weighing yourself weekly or measuring body composition. If you’re training for an event, maybe you keep track of your pace or how much weight you can lift. Some people might want to analyze their stress or sleep levels, using biomarkers like heart rate variability (HRV) to get a sense of their daily fluctuations in recovery status. If you make a big lifestyle change, feedback is crucial to assess progress toward your goal and modify if necessary.
One big lifestyle change that’s becoming popular is practice of ketosis—the physiological state where ketone bodies are elevated in the blood.
Ketosis can be achieved in two ways.
Most often, ketosis is achieved by eating a low-carb ketogenic diet, but it can also be “induced” by ingesting exogenous ketone supplements or ketone precursors like MCT oil and MCT oil powders.
Ketosis is so popular because it is thought that the shift towards burning fat for fuel that is part of this diet is preferential compared to burning carbohydrates and glucose that allows for both fat loss and improvements in the lipid panel-cholesterol and triglyceride concentrations in the blood.
Many who go keto eventually choose to measure their ketones. There are several reasons why measuring ketones can be beneficial.
For one, ketone levels can serve as a biomarker for the effectiveness of your ketogenic diet. If you want to know if your diet is really getting you into ketosis, then measuring ketones is the only way to do so. In addition, measuring ketones during a fast or after exercise can give you an idea of how your body responds to these interventions.
Another advantage of testing ketone levels is to gauge the effectiveness of exogenous ketones or see how your body responds to these supplements. This may give you some data on how long it takes for you to enter ketosis post-consumption, and how long ketosis lasts.
Quantitative feedback about your state of ketosis is a great way to provide transparency into your body’s response to a keto diet or exogenous ketones. High ketone levels are verification that you’re doing things right—or wrong (if they’re low or nonexistent). For instance, as a general rule, true “ketosis” is said to be when blood levels of beta-hydroxybutyrate (BHB) reach >0.5 millimolar (mM). Anything below that, and you’re not in ketosis. Testing for ketones is like your ketosis measuring stick.
Measuring ketones can also be a fun way to “gamify” keto. While this may result in the often-criticized act of “chasing ketones,” it may increase the adherence to keto.
Finally, the ability to measure ketones allows you to find and tailor your ketosis sweet spot. While the “optimal” level of ketosis is probably not the same for everyone, a blood BHB of 1.5 - 3.0mM is said to be ideal or weight loss. A “lighter” ketosis level of between 0.5 - 1.0mM is still sufficient for weight loss but is less extreme. If you know where you’re at on the spectrum, you could alter your diet or activity levels to get to the level of ketosis you want.
Long story short, if you have certain health or performance goals related to keto, testing for ketones is a must! Below, we explore you the three ways to test for ketosis, along with the pros and cons of each. We also provide a few ketone testing meters in each category to consider.
How to Get Into Ketosis
So you want to measure ketones? First you have to get into ketosis. Ketosis can be achieved in two ways — endogenously or exogenously.
Endogenous ketosis involves your own body’s production of ketone bodies. In this case, you’re “ketogenic”; your liver is making and releasing ketones into the circulation.
Eating a ketogenic diet is one way to get into nutritional ketosis. Restricting carbs and eating a high-fat, moderate protein diet is the combo our body needs to start producing ketones — carbohydrate restriction results in low blood glucose levels, keeping insulin low and allowing stored fat to be mobilized for energy. Eating a high amount of fat is essential, as fat serves as a substrate for ketone metabolism.
A second way to get into ketosis is to fast. Intermittent fasting — going anywhere from 18 to 48+ hours without food — is a surefire way to boost endogenous ketone production.
Prolonged endurance exercise (>90 minutes) also increases ketone production in humans. This might be especially true if you’re exercising in a fasted state.
In contrast to endogenous ketosis, exogenous ketosis occurs when you ingest an exogenous ketone supplement. These can include MCT oil, ketone salts, and ketone esters. Just 30 minutes after taking a BHB monoester, blood beta-hydroxybutyrate (BHB) levels can increase to 2.8mM.
Exogenous ketones allow you to get into ketosis even in the absence of carbohydrate restriction, fasting, or exercise.
Now that you know how to get into ketosis, it’s time to talk about the ways in which ketones can be measured.
Blood Testing for BHB
First, a short primer on beta-hydroxybutyrate, or BHB for short. BHB is considered to be one of the three “physiological” ketone bodies that are produced by the body and burned by our cells for energy.
BHB is produced in several steps. In a fasted or carbohydrate-restricted state, our body breaks down free-fatty acids (FFAs) and ships them off to the liver. Here, FFAs are turned into acetyl-CoA and then condense to form another ketone body known as acetoacetate (AcAc, discussed later). Acetoacetate is chemically “reduced” in the liver by enzymes to produce BHB. BHB then exits the liver and can travel through our circulation.
This is why we can measure BHB in the blood.
Why measure BHB?
Blood ketone levels BHB are the best and most accurate measure of ketosis since it measures BHB, the ketone body found at the highest levels in the blood.
Blood BHB is the preferred measure of ketosis because blood levels accurately represent what our body will be using. This is in contrast to other methods discussed below, which measure ketones that we are excreting.
How is BHB measured in the blood? It involves using a blood glucose or blood ketone meter—what you measure is dependent on the type of strip you insert. Many monitors available allow you to enter blood glucose test strips or blood ketone test strips. Some blood glucose meters can measure ketones, while some are glucose-only (keep this in mind when shopping!).
People with diabetes often test for blood BHB in order to avoid a condition known as diabetic ketoacidosis (DKA). This is a pathological state of high ketones and high blood glucose. It’s necessary for these people to measure glucose and ketones to avoid this potentially fatal condition. However, if you don’t have diabetes, DKA is extremely rare, and not something you should worry about on a ketogenic diet.
BHB measurement is pretty easy once you have the equipment. To measure BHB, you’ll need to purchase a ketone meter (or blood glucose meter capable of reading ketones), ketone test strips, a lancet device and lancets (to draw blood from your finger), and an alcohol swab to sanitize the area.
To take the measurement, follow these steps:
- Insert a lancet into the lancing device and set your desired puncture length
- Insert a test strip into the ketone meter
- Clean your fingertip with the alcohol swab to sterilize
- Place the lancing device on your finger, and press the button to puncture
- Gently squeeze your finger to get a reasonably-sized drop of blood.
- Touch the strip to the blood sample and allow it to absorb onto the strip
- Wait a few seconds, then analyze
Here’s a video demo of the process, with our co-founder and COO, Michael Brandt.
Advantages of Testing for Blood BHB
Blood BHB testing has several advantages. As stated earlier, it’s the most accurate measure of ketosis using “at home” commercial devices. If you’re looking for the most robust indication of whether or not you’re in ketosis, blood BHB testing is the way to go.
Another advantage may be the fact that by purchasing a blood BHB meter, you’ll also have the capability of measuring your blood glucose, if desirable. You can measure two outcomes with one meter — getting more feedback on how your diet and lifestyle habits are influencing your metabolism.
Disadvantages of Testing for Blood BHB
Blood testing may have some disadvantages as well. For one, purchasing a meter and test strips can get costly, especially if you test often. For those who are a bit squeamish around blood, the (minimal) invasiveness of this test might be a downfall of this method.
When you should test might just be up to personal preference, or what you’re trying to measure. Post-meal ketone readings are great to see how food impacts your ketone levels. In the morning after a night of sleep/fasting could also be a good time to take this measure. If you want feedback about how your diet is impacting your body over time, then be sure to measure at a consistent time of day.
Best Ketone Meters to Test for BHB
Does measuring blood BHB sound up your alley? Here are the 3 best ketone meters on the market.
Keto Mojo Blood Test Ketone Meter
The Keto-Mojo blood test ketone meter is probably the most popular meter on the market for measuring blood BHB. It measures both ketones and blood glucose, as well as blood oxygen.
The Keto-Mojo device is FDA approved for blood ketone testing—A definite plus.
The company has recently released an all-new feature for the product to make ketone tracking and monitoring easier. Keto Mojo can be paired with the company’s Bluetooth connector and app, which enables instantaneous syncing of your blood ketone and glucose levels right to your smartphone.
In terms of price, the Glucose and Ketone Meter - Basic Starter Kit can be purchased online for $44.99. This testing kit bundle includes the Keto-Mojo glucose and ketone meter, 10 glucose test strips, 10 ketone strips, and a clamshell accessory bag with a lancet device and 20 lancets. A replacement pack of 60 ketone test strips costs $48, and the blood glucose strips cost $13.99 for the same number. Keto-Mojo have created a "Combo Pack" which contains 60 glucose strips + 60 ketone test strips and costs $55.99.
Fora 6 Bluetooth Blood Ketone Meter
The Fora 6 Bluetooth Blood Ketone Meter (Fora Care Inc.) tests blood ketones and blood glucose—similar to the Keto-Mojo device. The Fora claims to be “easy to use” and is FDA approved. The device also has built-in Bluetooth technology, an LCD backlight, and uses Fora’s “advanced and innovative” Gold Advance Strip Technology which they claim assures accurate and reliable ketone readings.
You can purchase a Fora 6 Connect starter kit for $59.99. This includes the Fora 6 Connect meter, 20 ketone testing strips, 100 Fora lancets, a lancing device, owner’s manual, and carrying case. Additional ketone test strips can be purchased online for $53.99 (50 strips).
Precision Xtra Blood Glucose and Ketone Monitoring System (Bace Labs, Abbot Pharmaceuticals)
The Precision Xtra meter is one of the first meters to be used to monitor ketosis. Similar to the first two devices, the Precision Xtra can measure both blood ketones and glucose—though you still need separate strips to do so.
You can’t buy the Precision Xtra straight from the manufacturer, but a kit can be purchased online (Amazon) for $67.97 and on the Bace Labs site for $65.97. The kit includes the Precision Xtra monitoring kit, alcohol wipes, a one-month supply of lancets, and 10 Precision Xtra ketone test strips. Plus, they throw in an “I love keto” sticker.
Urine Testing for AcetoAcetate
Before going into this testing method, let’s talk about what acetoacetate (AcAC) is and why we can measure it in the first place.
Similar to BHB, AcAc is a ketone produced during fasting or carbohydrate restriction. In fact, AcAc is known as the only “true” ketone body, as far as chemical structure goes.
Acetoacetate is produced in the liver from fatty acids. While a lot of AcAc is converted to BHB, some AcAc also goes into the circulation. So why don’t we measure AcAc in the blood?
It turns out, at higher concentrations of ketones or before our body can fully utilize all of the ketones we produce, some ketone bodies fail to get reabsorbed by the kidney’s filtration system. These ketones are then excreted in the urine. Through specific measurement techniques, we can then measure the level of AcAc in the urine and use that as a proxy for how much fat our body is using and how many ketones it’s producing.
It may seem like measuring AcAc is less useful than BHB. While BHB levels are a more accurate measure of ketosis, urine testing is still valuable. Studies have shown that at lower levels of ketosis, urinary ketones correlate well with blood BHB, but may become less accurate at higher values.
The process of measuring urine ketones is relatively straightforward. All you need is special urine ketone test strips. To measure, you place the test strip in a stream of urine or a urine sample, wait 15 seconds, and then match the color on your strip to the color palette on the test strip container.
While different brands may have different color codes, a dark purple color is typically used to indicate the highest level of ketones. Most kits will also have a color that corresponds to a “negative” reading, which means no ketones were detected.
Advantages of Testing for Urine Ketones
Advantages of urine ketone testing are that it’s an easy, quick, and more cost-effective way to measure ketones. Urine test kits are available for purchase over-the-counter at most drug stores, and the strips usually cost around $10 for a pack of 100.
If you’re new to the keto diet or have never been in ketosis (or tried), urine strips are probably most advantageous, because they’re more accurate in measuring ketones before keto-adaptation occurs.
Disadvantages of Testing for Urine Ketones
Urine testing has its downsides, though. For one, urine ketones are a less accurate measure of ketosis than blood BHB. Urine testing is also influenced by factors like keto adaptation (accuracy decreases over time) and hydration status.
In contrast to blood BHB, urine test strips only give you a “qualitative” assessment of ketosis rather than concrete numbers. You’re typically provided with a reading levels of “trace,” “moderate,” and “large” amounts of urine ketones. This is different than the exact number you’d get when testing blood BHB.
Urine test strips may also not be ideal for measuring ketosis achieved using exogenous ketones. This is because ketone supplements rapidly raise blood BHB to high levels—most of which will be metabolized as fuel rather than excreted.
The final disadvantage is one we’ve already touched upon. Since we’re measuring AcAc levels in what is essentially a “waste product” of our body, this isn’t telling us anything about the ketones our body is using.
When should you test for urine ketones? There have been a few studies done to determine the ideal time for testing urine ketones specifically. They conclude that the reliability of urine ketone testing increases if tests are done early in the morning or in the late evening, several hours after dinner.
Best Ketone Strips for Urine Testing
If urine testing for ketones is something you’re interested in, take a look at some of the most popular brands.
One Earth Health Ketone Test Strips
One Earth ketone test strips are manufactured in the USA in an FDA-inspected facility. They’re also medical-grade and come with a lifetime warranty and a 100% money-back guarantee. For $12.99, you can purchase 150 test strips.
Smackfat Ketone Test Strips
These strips are made specifically for the keto diet and designed to accurately measure ketones. You can get a pack of 100 ketone test strips online for $6.95 from Smackfat.
Ketostix
Ketostix are the O.G ketone test strips—they’ve been around for quite some time. Ketostix are a popular go-to brand for testing urine ketones, providing similar benefits to the brands listed above. You can find Ketostix at local pharmacies for $10.99, which gets your 50 ketone test strips.
Breath Testing for Acetone
What is acetone? The “third” of the ketone bodies, acetone is produced when acetoacetate undergoes a chemical conversion, also resulting in BHB production.
While some acetone is used in metabolism, a majority is excreted in the breath. Fun fact—this is the reason for “keto breath.”
Since we breathe out acetone, we can use special devices in order to measure the amount of acetone in our breath. It’s basically a breathalyzer...but for ketones.
Is measuring acetone of any value? The answer is probably yes. While not as accurate as measuring blood BHB, breath acetone concentration correlates well with fat metabolism. Studies have shown that as breath acetone levels increase throughout a diet, fat loss increases.
Ketone breath meters are relatively new products on the market, but are destined to become one of the more popular consumer devices for measuring ketones.
Advantages of Testing for Breath Acetone
Breath acetone measurement is probably the easiest method of the three — because it is probably the most convenient. Just do something you do all day, every day: breathing.
Along with the ease of measurement, other advantages of breath ketone testing are that the cost is virtually zero after purchasing the device. You don’t have to buy strips, lancets, or other accessories.
Disadvantages of Testing for Breath Acetone
Breath testing has some downsides though.
For one, you need to keep the device on you at all times. Most of them are quite small—about the size of a pen—so this isn’t a huge issue. Breath ketone testing may also be less accurate measure of whole-body ketone levels than BHB. Furthermore, similar to AcAc, when we measure breath acetone, we are measuring a waste product, not the ketones our body is using. However, it does give you an idea of fat-burning capacity at any point in time.
When should you test? Breath ketone meters allow you to test virtually anywhere at anytime, and most of the companies selling the devices encourage frequent testing and testing in response to things like food, exercise, and fasting.
Top Breath Ketone Meters
Breath sensors are some of the hottest ketone-testing devices on the market. If you’re interested in this method of testing for ketones, here are two recommended meters.
Keyto Ketone Breath Meter
The Keyto device is designed to help those who use it to gauge how much fat you’re burning at any one time as well as answer the question of whether or not you’re in ketosis.
Keyto was founded by Ethan Weiss (who’s appeared on the our Podcast), an expert cardiologist who is interested in the metabolic benefits of the ketogenic diet. Keyto has gone through numerous lab calibration tests to achieve high reproducibility and accuracy for each device.
How does it work? The device contains metal oxide nanoparticles, which react with oxygen (in the air) and other gases—including acetone. Acetone causes changes in conductivity which can be read by the device, turned into a digital signal, and transmitted through the device and into the Keyto App. The app then gives your “Keyto Level” to indicate your fat metabolism and estimated level of ketosis.
Keyto can be purchased for $99 on the website for the device only. The company also sells a “Keyto Premium” pack for $195, which includes the Keyto device and premium app access, recipes, personalized meal plans, an MD-approved food guide, and a free Keyto food box which they value at around $80.
Ketonix Ketone Breath Meter
Ketonix is one of the original breath ketone meters designed to instantly measure breath acetone to tell you how much fat your body is using. This device allows you to measure ketones on the move, or anywhere you like.
One cool feature of Ketonix is that the Ketonix app provides a “moving average” of ketone levels, which make it easy to see times during the day when ketones were low or high, allowing you to adjust things as you see fit.
Ketonix can also connect to a cloud computing network known as Heads up Health, which uses data science, machine learning, and advanced analytics to identify patterns that are unique to your own physiology. This database also has global data sets to which you can compare your own data. Pretty neat.
The new 2019 Ketonix Bluetooth device is $219 on the Ketonix website. It’s the latest version of Ketonix and is supported on iOS, Android, Mac OS, and Windows.
Choosing the Right Ketone Meter for You
You might be overwhelmed with all of the choices available to you for testing ketones. Several different blood, urine, and breath meters exist, and all of the testing methods have their advantages and disadvantages. It’s safe to say that one ketone meter won’t work best for everyone.
So, how do you decide?
The specific testing method and ketone meter you choose should depend on your goals; what kind of information do you want, and what outcomes are you looking to achieve? If you’re really just interested in an answer to the question, “Am I in ketosis?,” then any meter might work well.
If you want a more robust and fine-tuned reading of your ketones in response to a ketogenic diet or other lifestyle changes, than a more accurate (yet invasive) testing method like blood testing might be best for you. If you’re new to keto and are looking to test the effectiveness of your diet, then breath testing may be the way to go.
Consider what you’re willing to pay, how convenient you want testing to be (or how invasive), and which ketone meters will fit best within your lifestyle.
Your journey may eventually lead you to trying all three testing methods to see which suits your style. In any case, measuring ketones is a fun and rewarding way to be an effective biohacker, or just to start taking control of your health.
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