Motivated by numbers and data? You’re not the only one. Biometrics like blood glucose (blood sugar) and blood ketones can provide immediate and ongoing feedback for people following a keto diet. The glucose ketone index (GKI) is a simple calculation that can make it easier to understand these numbers.
Individually, blood glucose and blood ketone levels can give you a fair picture of your metabolic health. Still, there are some disadvantages to relying on just one of these. They can both be affected by several factors, like stress, sleep, or how recently you’ve eaten.
The GKI uses these numbers to provide a more useful indicator of your body’s ability to burn fat.
Here’s a guide to the glucose ketone index, how to measure it, and why it matters.
What is the Glucose Ketone Index?
The glucose ketone index (GKI) provides a snapshot of the relationship between your glucose and ketone levels. It helps you determine how “deep” your level of ketosis is. Ketosis is a metabolic state in which your body turns to ketones from fat as its primary fuel source, rather than carbs (* , *).
There are varying degrees of ketosis, and two key factors that affect your level of ketosis are fasting and carb intake (*).
The GKI is one number that helps you determine your degree of ketosis. It’s simply an expression of the ratio between your glucose and ketone levels (*).
The GKI formula is:
(Glucose in mg/dL ÷ 18) ÷ Ketones in mmol/L = GKI
If your glucose reading is already in mmol/L (which is likely, if you’re not in the U.S.), here’s your GKI formula:
Glucose in mmol/L ÷ Ketones in mmol/L = GKI
Why the Glucose Ketone Index Is Important
Many people who follow a ketogenic diet are interested in knowing their level of ketosis. Here are some examples of who may benefit from knowing their GKI:
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Shop Best Sellers- Weight loss: GKI can help you determine if your body is becoming more efficient at burning excess fat (*).
- Fasting: GKI can also be used to monitor fasts. For example, you can use GKI to determine when you enter ketosis and to set a target for breaking a fast.
- Insulin resistance: Ketogenic diets may help improve insulin resistance. Checking your own GKI can be helpful in monitoring metabolic health if you have type 2 diabetes, polycystic ovary syndrome (PCOS), or other conditions associated with insulin resistance (* , *).
- Neurological disease: Ketogenic diets have been used for decades, with great success, for neurological disorders like epilepsy. In these cases, a therapeutic level of ketosis is often required (*).
- Cancer: Therapeutic ketosis may also be helpful for certain types of cancer. Typically, a healthcare team will strictly monitor these cases (*).
- Athletic performance: Many athletes are experimenting with nutritional ketosis or supplemental ketones for optimal performance, and GKI may be a helpful tool (*).
- Longevity/overall wellness: Finally, a low level of nutritional ketosis may be optimal for longevity and overall health — so even if you don’t have more defined health goals, you may want to check your GKI occasionally (*).
Factors Affecting Glucose Ketone Index
Several factors may affect your glucose and ketone levels, which therefore may also affect your GKI: (* , *, *)
- Diet and macro composition
- Amount of food you eat in a sitting
- Total calorie intake
- Health status/medical conditions
- How recently you’ve eaten
- How recently you’ve exercised
- Fasting status
- Stress levels
- Sleep quality
- Use of exogenous (supplemental) ketones
- Use of certain medications
With all of these different factors that can affect GKI, it’s a good idea to check your GKI under similar conditions each time.
How to Calculate Your Glucose Ketone Index
Ready to calculate your glucose ketone index level? You will need a testing device capable of testing both glucose and ketones, along with alcohol wipes, lancets, and glucose and ketone testing strips.
Ideally, 2–3 hours after eating is the best time to check your glucose-ketone index. Testing too soon after eating, or waiting too long after eating to test, may both affect your results (*).
Here are the steps:
- Follow the manufacturer’s instructions for your testing device to check your glucose and ketone levels. Make a note of them.
- Calculate your GKI using the formula above, or plug your data into a GKI calculator.
- Interpret your results using a chart like the one below.
Glucose Ketone Index Calculator
Enter your blood glucose in (mg/dL) or (mmol/l) *
Enter your your blood ketones *
How to Interpret GKI Results
This table, adapted from KetoMojo, can help you interpret your GKI results: (*)
| GKI | Interpretation | Best for |
| 9.0 or greater | Not in ketosis | N/A — this level indicates that you’re not following a keto diet or only recently started |
| 6.0–9.0 | Mild ketosis | Weight loss and optimal health |
| 3.0–6.0 | Moderate ketosis | Metabolic conditions like type 2 diabetes, insulin resistance, and obesity |
| 1.0–3.0 | Therapeutic ketosis | Dietary management/treatment of cancer, neurological diseases, and chronic inflammatory diseases |
| 1.0 or less | Highest degree of therapeutic ketosis | N/A — this level is generally only attainable under strict, medically supervised ketogenic diets |
Frequently Asked Questions
How often should I test my GKI?
According to a 2015 study on using the GKI for brain cancer, GKI should be measured twice daily, and each measurement should take place 2–3 hours after eating (*).
However, glucose and ketone test strips can be costly. If you’re not testing GKI for the management of a severe condition such as brain cancer, you may want to consider testing less frequently.
For instance, if you’re trying to lose weight, taking one GKI measurement per week (on the same day of the week, at the same time, after the same meal each time) can be a helpful way to measure your progress.
How can I lower my GKI results?
Lowering your GKI results can take time. Especially if you’re brand new to eating keto, it may take several weeks for your body to fully shift into a state of ketosis.
Therefore, the most reliable way to lower your GKI results is to consistently stick with a keto diet.
What is the ideal GKI for weight loss?
The ideal GKI for weight loss is anywhere between 3.0 and 9.0. If you have a lot of weight to lose, or have obesity along with other chronic health conditions, you may benefit from a lower GKI level — which indicates a deeper state of ketosis (* , *).
However, if you only have a little bit of weight to lose or no other health conditions, a GKI from 6.0 to 9.0 is a good range.
The Bottom Line
Glucose ketone index (GKI) can be a helpful tool for determining your level of ketosis.
Depending on your health goals or purpose for following a ketogenic diet, you may want to aim for a milder or more therapeutic level of ketosis.
To calculate your GKI, all you need is a ketone reading and a glucose reading, taken 2–3 hours after eating.
The glucose ketone index is a valuable data point that can help you better understand your metabolic health and track progress toward your goals.
When to take our GKI? Morning? Evening? Time of day changes the GKI importantly…
Take it anytime you would like to know your GKI. To track trends, take it at the same time of day over time.
I have an iPhone app called KetoLogger that, once you enter your glucose and ketone #’s will calculate (and log) your GKI. I find the app handy to use.
Great info. Thanks!
I’ve just started using this app too, what a great measuring tool! I’m running from 1.9 to 2.2 for three days.
Very coo. I have my iPad. I’ll look now and put that on It
Is it neccessary to track glucose with ketones?
Hmm haven’t heard this before?thx
Hey Dan, it’s not completely necessary but it’s a useful tool depending on what your goals are.
My average KGI over my last 25 blood glucose Ketone readings is 1.2!
Has anyone consistently had great GKI numbers but no weight loss? I am at an average of .9-1.9 GKI for the past 30 days and the scale is not moving!
I would pay attention to body compensation rather than scale numbers. You gain muscle while in ketosis so the scale may not always move but your measurements may be different.
Has anyone had a problem with very high glucose readings even after a 12 hour fast? Mine is consistently 140-162. I have never had blood glucose readings that high even while eating a moderate carb, low fat, moderate protein diet. Ive been on this diet for a month now and can’t imagine my liver being able to consistently dump that much glucose out. I stay in the small ketone range as well.
I am also diabetic and can tell you that I cannot fast successfully either. I have to keep an even supply of food in my system or my blood sugar either goes too high or too low, whichever it feels like doing. That’s why dieticians tell you to eat 6 small portions of food per day instead of 3 larger. To try and keep your blood sugars even.
If I were you, I would take information from the keto diet. But also read Dr. Aitkins diet revolution book! He suggests not going 3-4 hours without eating! I successfully lost 103 pounds! Exercise and carb control is the real key!
At one month of Keto, you are probably not “fat adapted” yet. You are in ketosis, but not fat adapted. From what I have read, if your body is not tolerating the fasting yet, you should try again in a few weeks. The average to become fat adapted varies, but generally it is 6-8 weeks.
My goal is weight loss. But I am at 2.9 GKI which this article indicates is the level for disease prevention which is great. But is that level still good for weight loss? I am consistently losing but I am curious in the levels.
Hi so I have been low carb for a month and a half. I just bought a ketone/blood sugar monitor and took my fasting measurements in the morning as 92BS and 1.2Ketone. After eating dinner I decided to retest and my BS126 and 2.6Ketone. Should I be concerned about this BS increase even though my GKI is 2.6? This was taken about 30minutes after eating too.
That’s perfectly fine. (As long s you are not diabetic)
A post meal glucose level can be anything from 110-140 approx an hour after eating. Your ketone level is excellent considering you have only been on a ‘low carb’ diet for a month (are you trying for full ketosis or just low carb?) For your info it has taken me 9 weeks to become fat adapted, which I am finding amazing by the way!
My average ketone level is 3.8 and average GKI is 1.62. Stick with it, keep an eye on your macros, change accordingly and enjoy.
My macros at present are Fat-75% (155g), protein-20% (100) and carbs-5% (15g).
Hi can anyone tell me how long it took to show up ketones? i’m on day 5 of keto and nothing yet
Easier: Calculates it for you: http://perfectketo.com/glucose-ketone-index-calculator/
The idea that if you’ve got a GKI over 9 you’re not in fat burning mode is utterly ridiculous. Many times I have had a gki over 9 and ketones of 0.5mmol/l or over over. If you have ketones at or above even 0.3mmol/l you are obviously burning fat. GKI is not a pure measure of fat burning but the proportion of glucose to ketones. Fat burning is only related to ketones. There are many examples of fat adapted athletes who have ketone levels of just 0.3 to 0.4 mm per litre, one who was a boat rower crossing the channel on an 80% fat diet. Are you telling me they are not burning fat? Idiot. If a high GKI is due to a high blood sugar, this could well mean a lack of utilisation/uptake of glucose, for example after a postprandial measurement,
or it could indicate insulin resistance. What it does not indicate is that there is no fat burning going on and if there were ketones in the blood then obviously there’s fat burning. You shouldn’t put information on like this because it will push people towards more and more extreme forms of dietary control at the expense of a broad range of nutrients, for example going below optimal protein or having such a small carb allowance that even green vegetables and nuts become an unaffordable luxury. See the leading researchers follow company who don’t ever mention the gki index and rather suggest that nutritional ketosis begins at 0.5 mmol/l and optimal ketosis between 1 and 3 mmol per litre. I get so angry with this pervasive, insidious miss information even on allegedly well-informed sites like this. Well it is not well informed. This website feignes to be expert in something it isn’t. Go to Virta health’s website into faultless, research backed information from the leading ketogenic diet researchers and authors that will not mislead.
Hi Aaron, we see your frustration but would like to clarify a few things. It is important to note that the GKI isn’t the only factor in ketone levels. We actually agree that nutritional ketosis starts above 0.5 mmol/l. However, for your GKI to be above 9, your glucose levels would have to be so high that we would not consider your body to be in a fat burning state. Keep in mind that when you are testing ketones and glucose in the blood, you are getting a snapshot of what is currently available in the blood, or what your body has already done, not what it is currently doing.
When your blood sugar rises, especially to the degree to get your GKI over 9, your body is going to shut down fat burning unless you are suffering from insulin resistance like you said or potentially prediabetes. That doesn’t mean that your body didn’t burn fat and produce ketones prior to that major elevation in blood glucose, which is why you may still see residual ketones in the blood when your blood glucose is that elevated or again it could be a sign of insulin resistance.
In general, we know that in the healthy body, if enough blood glucose is available (which a GKI over 9 would be much more than enough) then the body is going to really slow or completely halt fat burning because the necessity is not there.
We hope this clears up some confusion and if you have any other questions please do not hesitate to ask.
I recently started keto 8 weeks ago. I lost 9 lbs in the first 2 weeks albeit water was a big part of that, for the next six weeks danced around that number.
My fasting glucose rose in the mornings around week 7. I was shocked!
I felt great my skin looked way better. All of my aches and pains went away. So i just kept on going.
With the high fasting numbers my ketones dropped to .2 to .4 but i kept going.
Week 9 my fg came down into the 70s to 82 range. Ketones up but not as high as during the first 6 weeks where i would reach 2 to 4 mmols. I am losing again.
In week nine 5 lbs. My gki ratio is way better even at lower ketones. Why you ask? You can’t use you stored fat if insulin is produced constantly. I believe in the beginning I was making high ketones from the fat i was eating, which is great. I was full and this allowed me to implement IF (intermittent fasting).But for me it took some time to burn thru all of the liver stores and heal metabolic syndrome.
Hi. I have been on KETO for 7 weeks. I have had positive results, lost inches, clear skin, energized, mood enhanced, and increased energy. However, weight loss is super slow. I know that I do have insulin resistance/PCOS. I recently started metering my GKI and the number is always high 8 or over. My KETO says between .4 and the highest is 1.1. Reading Aaron’s post and Clarisse’s response insulin resistance is the exception to all the KETO rules. What exactly does this mean? Is weight loss illusive? Should I follow a different KETO protocol? I would love to lose 20 pounds. Also, I upgraded to measuring blood instead of urine, because the urine strip never went up the trace or small color indicator. Any assistance would be appreciated.
Becca, do not be discouraged! If you are insulin resistant, it may just take your body a little longer to adjust to this new diet. If you are keeping your carbs in check and adding exercise then you are doing the right things. Stick with it and the weight loss will come, it takes your body time to repair itself.
Dear Gem.
I was very strict with my keto diet and it took me 10 days to reach ketosis.