The Keto diet is unique. Unlike other diets, it has a measurable biomarker for success: the ketone.
By measuring your ketone levels, you can determine if you’re burning fat on Keto. It’s instant validation.
Because of this, some people become obsessed with ketone levels. If their ketones aren’t high enough, they think they’re failing.
But that’s not necessarily the case. It’s not a competition, and higher ketone levels aren’t always better.
So what should your ketone levels be? There isn’t a stock answer to this question. The answer will depend on your goals.
We’ll dig into numbers in a minute. First, though, let’s talk ketones.
What Are Ketones?
Ketones are molecules produced by beta-oxidizing (burning) fatty acids in your liver.[*] Once in circulation, ketones fuel your brain, muscles, and other tissues.
Ketones have an evolutionary purpose. Our ancestors were often short on carbohydrates, which meant their levels of blood glucose (our default brain fuel) would fall.
That’s where ketones came in. In the absence of glucose, ketones supplied the brain with energy. They’re backup brain fuel.
This backup energy system is fairly simple to unlock. When you restrict carbs on a Keto diet, the hormone insulin stays low. Low insulin, in turn, signals your liver to burn fat and produce ketones.[*]
There are three types of ketones, also called ketone bodies:
- Beta-hydroxybutyrate (BHB)
- Acetoacetate
- Acetone
BHB and acetoacetate both supply energy, while acetone is a seemingly useless byproduct of fat metabolism[*]. When people talk about “ketosis” or “elevated ketone levels”, they’re usually talking about elevations in BHB.
What Level of Ketones Indicates Ketosis?
Ketosis means that ketones are elevated in the body, usually in the blood. But what level of blood ketones officially marks ketosis?
It depends who you ask, but the general consensus is that ketosis starts at 0.5 mmol/L BHB.[*] This is, to be clear, a measurement of beta-hydroxybutyrate circulating in the blood.
Nutritional ketosis refers to the type of ketosis promoted by a high-fat low-carb Ketogenic diet. As a general rule, nutritional ketosis starts at around 0.5 mmol/L and ends around 3.0 mmol/L.
Above 3.0 mmol/L and up to about 7 or 8 mmol/L is still physiologic,[*] but one enters the realm of medically therapeutic ketosis. These higher levels of ketones are usually achieved by fasting, protein restriction, exercise, exogenous ketone supplementation, or some combination.
When ketone levels rise above 7 or 8 mmol/L, it may indicate a dangerous condition called ketoacidosis.[*] (Note: ketoacidosis may begin as low as 3 mmol/L for type 1 diabetics). Ketoacidosis primarily plagues type 1 diabetics because they lack the proper mechanisms to shut down fat-burning. It’s rarely a concern for healthy people following a Keto diet.
Different Ketosis Goals
Your optimal ketone levels will depend on your goals. Different goals may require different ketone levels.
Ketosis for Weight Loss
If you’re using ketosis to lose weight, maintaining ketone levels of 0.5 mmol/L-3.0 mmol/L is probably your best bet. Multiple studies have found that staying in nutritional ketosis with a Keto diet may help with weight loss.[*]
For instance, in a 2018 study sponsored by Virta Health, researchers kept 218 type 2 diabetics in supervised nutritional ketosis for a full year.[*] When the year was up, not only had the patients lost an average of 30.4 pounds, but 60% had “reversed” their diabetes as measured by HbA1c, a marker of average blood sugar.
Nutritional ketosis promotes weight loss by at least two mechanisms. First, it indicates that you’re burning fat for energy. If you want to lose body fat, you want to be burning it.
Elevated ketones also have a suppressive effect on appetite. In one study, obese people on a low-carb diet ate fewer calories than obese people on a calorie-restricted low-fat diet, even though the Keto folks didn’t consciously restrict portions[*] Other studies also show spontaneous calorie reduction on Keto.[*][*] Less energy in, less weight gained.
Ketosis for Therapeutic Purposes
For goals such as stable energy, reduced cravings, weight loss, and mental clarity, you’re best served by maintaining nutritional ketosis. But what if you’re using ketosis to manage a specific medical condition?
In fact, the classic Ketogenic diet was originally developed back in the 1920s as a treatment for childhood epilepsy. Higher ketone levels were correlated with fewer and less severe seizures.[*]
Along with epilepsy, ketone levels above 3 mmol/L (up to around 8 mmol/L) may be therapeutic for conditions such as cancer, neurodegenerative disease, and autism.[*]
A quick disclaimer. Be sure to work with a medical professional if you’re using ketosis to manage any medical issue.
Measuring Ketone Levels
You can measure ketones in the blood, breath, and urine. Blood ketone readings are still the gold standard, but breath readings are catching up with devices like the BIOSENSE® breath ketone meter that measure acetone in the breath. (Breath acetone levels are correlated with blood BHB levels).[*]
What about blood ketone measurements? Check out the Keto-Mojo meter. It measures blood glucose along with ketones and syncs with your smartphone (plus the Carb Manager app) for easy tracking.
How Often Should You Test Ketones?
First, remember that it’s not strictly necessary to test ketones at all when you’re following the Keto diet. Many (maybe even most) Keto aficionados gauge whether or not they’re in ketosis based on what their body is doing and how they feel. Reduced hunger and more energy? You’re probably in ketosis!
Biohackers and followers of the “precision nutrition” movement test their ketones following every meal to get a sense for which foods and activities correlate to different levels of ketosis for their particular bodies. The BIOSENSE® breath ketone meter promotes this type of testing, and users of BIOSENSE + Carb Manager can actually cross reference this information right in the Carb Manager app.
But most people following a Ketogenic way-of-eating find testing multiple times a day to be overkill. It’s a lot more typical to test once a day over the first couple of weeks, and then once a week after that. This schedule provides reassurance that you’re on the right track without feeling like you’re constantly taking measurements.
Why Ketone Levels Aren’t Everything
When you measure your ketones and get a positive result, it can be a real confidence booster. It says you’re going in the right direction.
Taking the interpretation beyond that, however, may be problematic. First of all, science still hasn’t figured out the optimal level of ketones. We can say with some confidence that you don’t want 0 mmol/L BHB (which means you’re probably not burning fat), and that 0.5 to 3.0 millimolar BHB appears to be the green zone for nutritional ketosis. But we can’t say that 1.8 mmol/L is better than 0.8 mmol/L.
In fact, some folks see declines in blood ketones over time on Keto, despite positive results in all other areas. Why is this happening? It might be a beneficial increase in ketone utilization. In other words, fewer ketones are in the blood because more ketones are being utilized by muscle and brain tissue. It might be a sign of Keto-adaptation.
In addition, lifestyle factors like fasting and exercise can impact ketone levels, temporarily skewing levels one way or the other.
Simply fasting overnight (in other words, sleeping) may cause ketone levels to rise by .1 to .5mM. Longer fasts of up to 48 hours of fasting may result in ketone levels of 1 - 2mM, even if you weren’t in ketosis beforehand. Extended fasts may increase ketone levels even further.[*]
Similarly, anecdotal reports suggest that anaerobic exercise may decrease ketone levels while aerobic exercise may increase them.
What Should Your Ketone Levels Be?
There isn’t a clear answer to this question. It depends on your goals, and perhaps your level of Keto-adaptation.
For most Keto goals, staying in nutritional ketosis (0.5 mmol/L-3.0 mmol/L) seems to make the most sense. But more therapeutic goals may benefit from higher ketone levels.
And remember, ketone levels aren’t everything. You didn’t go Keto to hit a certain level of ketones, did you? You went Keto to improve your health.
If you’ve been following Keto and aren’t seeing signs that your body is in ketosis—or you’re actually testing and not seeing your ketones trending upward—check out this article for troubleshooting tips.
Bottom line: pay attention to energy levels, appetite, sleep, bodyweight and other health metrics first—and ketones second. This approach will serve you well in your quest for health and happiness
Note: Individuals with a history of health conditions such as type 1 diabetes should consult a health professional prior to making any diet or lifestyle modifications.
Comments
BlithesomeArugula750680 3 months ago
I'm a 47 year old male, I'm 6ft tall, my optimal weight was always 180 lbs, the last few years it was slowly going up until I reached 195 and my fasting blood glucose was slowly moving up and reached 103, I was afraid that I'm heading towards diabetes, a few months ago I heard about Keto, low carb and Intermittent fasting, I started a 18/6 diet but my weight and my glucose didnt really budge, so I decided to increase fat and lower carbs, I wasnt on a strict keto diet but rather low carbs, and I started shedding weight, my glucose was still hovering around 100-104, about a month ago I bought a keto monitor and I measured 1.7, I realized that I'm in ketosis and decided to go strictly ketos, the last 3 weeks my glucose has always been under 94, and the past week it has been 83-84 and my weight has gone down to 165.
UpbeatCauliflower194618 5 months ago
I was one of those obsessed with ketone levels. First measured with strip ketones. Then shifted to blood ketone testing. But now I am wearing continuos ketone measuring device on my arm. So, what is the conclusion? Yes, low ketones are not always the sign that you are not making them! This may be the sign that you are actively using them! For example, when I am lying down and reading a book, my ketone levels im blood are steadily raising. They can even reach above 3 mmol. As soon as I engage in physical activities, their level start falling! The harder the physical activity, the more they fall! At first I was puprlexed, but then I realized that this is a good sign! My body makes ketones and uses them when necessary! Get yourself a continous ketone meter, it will really change your understanding of how and when your unique body makes and uses ketones!
semih_in_deutschland 7 months ago
On a 6 day streak of low carb keto diet, average 14 grams carb per day, losing 200 grams per day consistently. Measured my keton level is 4-6 mmol/lt (keton strips). This thing is the only method for me to get rid of body fat. 93.8 to 85 kg (18 pounds) in 40 days expected.
Tburnett 8 months ago
I’ve been doing low carb for a long time i intermittently fast and have used urine strips in the past but recently got keto mojo very seldom I register 0.1-0.8 thru the day but I’m the evening before bed I’ll test 1.0-3.0 I don’t understand am I going in and out of ketosis or what is happening? I’m not sure if I’m in ketosis or out My food log always looks good
SeaCat31 7 months ago
Food takes your keto level down even if you haven't consumed carbs. Ideally test before a meal or in the morning before breakfast
AwesomeKale225068 2 years ago
I appreciate the honesty of the article but it also seems to show how near-useless ketone testing is. If someone gets a low reading, for example, does it mean that they’ve been eating badly or need to exercise more? It’s impossible to say since even the author of this article states that low ketone readings can be the result of “keto-adaptation ”.
R.Lee.Big 2 years ago
I know when I'm in ketosis simply by how I'm feeling a attitude.
Gulfcoastal 2 years ago
I can't seem to get past .5 and I've regulated myself to under 17g carbs a day. Frustrating. Guess .5 is better than 0
wafa0002bc7d 9 months ago
I’m stuck around 0,3 even after 24h fast… i don’t understand why
Rass813 2 years ago
Higher intake of protein can swing the numbers lower. Also how long have you been strict keto?
MirthfulAvocado123067 2 years ago
What are your thoughts and advice on urine levels for testing ketones?
OutstandingArugula509254 2 years ago
Great article. You actually answered the question I was looking for. The fact that we do not know if 2 ketones is better than 1. As of now, ketosis is ketosis. At 16 hours of fasting I will be at 3.0+ and 1.7 in the am. I use Keto Mojo to spot check new foods.
FabulousCauliflower119878 3 years ago
I'm never under 3.0 and as high as 4.8 for the last 6 months. I'm Carnivor and OMAD. I use a Keto Mojo meter to measure my Ketones daily. Thank you for this great article I was worried my ketones were too high.
RemarkableKetone642270 3 years ago
If my urine ketones are 8mmol/l am i still losing weight? Or am i eating to much fat or to little carbs? I am not diabetic at all.
FantasticKale564736 3 years ago
I have the same question. I use the blood test and my keto levels are on 5. One week ago it was at 3.5. Is this dangerous that every week my keton levels going high?
MrsDuru 3 years ago
I'm wondering the same.. I use the urine one and I'm constantly dark purple and maybe once in awhile the shade lighter. I'm forcing myself to eat the macros I'm at not Andy I do IF as well. I'm losing weight and don't feel ill but dunt want to stall bc I'm doing something wrong or even worse harm myself by being too high and the blood becoming acidic as it can. Ive asked this question many times in many places and still haven't gotten any answer and can't find anything even on Google 🤦♀️
AwesomeKale691648 3 years ago
I don't measure my carb intake. I just eat very, very small amounts of carbs. When I do this I find that I keep getting headaches. Is this from too few carbs. I'm very new to this & not used to the diet.
Avacato 3 years ago
Use a ketone strips once a week after consuming too many carbs. I usually get out of ketosis for 24 hours after cheating.
OutstandingArugula509254 2 years ago
Takes me 24 hrs also
ken 3 years ago
I tested my ketones with the strips and read normal is that good or bad?
RousingRadish438496 3 years ago
Thank for this info!
Fxzbrn66 3 years ago
Good information, Wild, that Biosense meter is extremely expensive!!!
blhs 3 years ago
Yeah it is expensive, but my other ketone blow meter was cheap and is not accurate. I ordered a Biosense meter, and yes as a senior, it took a bite of my BA. I'm just waiting for it to be delivered.
PropitiousRadish363275 3 years ago
Thanks! The more education, the better.
Reachmygoal 3 years ago
Very informative!
#DeterminedNotDefeated 3 years ago
Great clarification for me!