A large part of success on the ketogenic diet is tracking ketone levels at the beginning.

Doing this helps you know if you’re in ketosis and, if not, where you may need to tweak your diet and macros.

But did you know there’s an even more accurate measurement? The Glucose Ketone Index (GKI).

The GKI is a simple calculation that allows you to find out how ketosis works best for you individually.

Today we’ll be looking at how to easily track your Glucose Ketone Index for different aspects of health.

What Are Ketones?

Ketones, or ketone bodies, are energy molecules made by your liver. Everyone has some level of ketones in their body even when they’re not in ketosis.

There are three types of ketones:

Here’s how ketone bodies are made: When you drastically cut your carbs, your body stops getting sufficient levels of glucose. Glucose is your body’s primary fuel source when not in keto.

This lack of glucose makes your body turn to glucose stores (glycogen), but when these get depleted, your body starts looking for alternative fuel sources. That’s when your cells start burning fat, transforming fat stores into ketone bodies in the liver. This process is known as ketogenesis.

When you have enough ketones in your blood that your body can use for energy, you’re in nutritional ketosis. When you’re starting keto, it’s hard to know when you enter ketosis, so that’s why you need to test.

How to Test Your Ketone Levels

To know your GKI, you must first test your ketone levels.

There are three different ways to get your ketone reading: through urine, your breath or your blood.

#1: Urine Ketone Testing

A ketone urine test is simple: You pee on a urine strip, wait a bit and see if any ketone bodies have been detected in your urine.

This is the most affordable, but least reliable way to test your ketone levels. Excess ketone bodies are excreted through your urine, and therefore this test does not measure the amount of ketones currently in your blood.

#2: Breath Ketone Tests

Ketone levels on your breath can be tested through a breath meter.

While this method is more accurate than urine testing, it’s still not optimal. Acetone, one of the three ketone bodies, is the one most commonly found in your breath. However, beta-hydroxybutyrate (BHB) is the ketone your body actually uses for energy and therefore the best ketone to measure how far you are into ketosis.

#3: Blood Ketone Testing

This the most expensive, but the most accurate way to test your ketone levels.

You simply prick your finger and use a blood ketone meter to measure the amount of BHB in your blood.

BHB is the most abundant ketone in your body and the one used for energy on ketosis.

What the Glucose Ketone Index (GKI) Is and How to Use It

Now that you know how to test your ketone levels, it’s time to better understand the GKI.

Developed by Dr. Thomas Seyfried, the GKI measures your glucose levels along with your ketone levels. This matters because even when you have high ketone levels, if your blood sugar levels are also high, you will not get the full benefits of the keto diet.

Researchers have used the index in multiple studies about the ketogenic diet and fasting to track changes and progress regarding weight loss, athletic performance, management of metabolic diseases like Type 2 diabetes and even cancer treatment.

Here’s how to use the GKI to your advantage:

What is the Glucose Ketone Index

#1: Track Your Ketone Levels and Blood Glucose Levels Simultaneously

The GKI lets you track both glucose and ketones at the same time, taking into account how they work together.

This is a better marker of your metabolic health than simply measuring ketone levels, because even if you’re deeply in ketosis, you could still have high blood glucose levels that throw things off and affect your health.

Knowing both measurements helps you make better health adjustments.

#2: Understand How Your GKI Correlates With Your Goals

You cannot classify a GKI number as “good” or “bad.” Rather, you need to understand how different numbers bring your closer to various health goals, such as weight loss, better overall health, or treatment of more serious conditions like Type 2 diabetes, obesity, or cancer.

Below are some fairly widely accepted glucose-ketone numbers for different conditions or treatments:

  • Anything above 9 means your body has not transitioned into a fat-burning state.
  • A 6-9 GKI demonstrates a low level of ketosis: This is appropriate for those who want to lose weight or maintain optimal health.
  • A 3-6 GKI demonstrates moderate levels of ketosis: This is appropriate for addressing many common metabolic diseases including insulin resistance, Type 2 diabetes, or obesity.
  • A less than 3 GKI is a high level of ketosis: This is typically used for addressing epilepsy and cancers. Entering this high level of ketosis periodically each year can be beneficial for anyone hoping to use ketosis for disease prevention.

To get the most benefits from ketosis, you want to get your GKI number as low as possible.

While you may use the GKI simply to tweak your macro guidelines, this measurement can als be used in a wide range circumstances, including:

  • Cancer Treatment: Researchers first used the GKI in the treatment of different cancers, especially brain cancer.
  • Diabetes Treatment: The index has been used with metabolic therapy for both the prevention and treatment of Type 2 diabetes and Type 1 diabetes.
  • Fasting: The GKI is a tool to see how your body responds to fasting, and whether intermittent fasting helps you enter ketosis.
  • Athletic performance: Those looking to increase their athletic performance can use the index to see how their body responds to using ketones, rather than glucose, during competition.

How to Calculate Your GKI

To get your GKI reading, here’s what to do:

Measure your glucose and ketones levels at the same time. To do that, you’ll need:

  • A glucose meter and strips
  • A ketone meter and ketone test strips
  • A calculator for some simple math

First, measure your blood glucose levels as described on your blood glucose meter. Then, do the same for your ketone levels, following the directions on the test.

Once you have both numbers, take your glucose number and divide it by 18 (this is to convert the blood glucose reading from mg/dL to mmol/L. If you’re not in the U.S. and the reading is already in mmol/L already, you don’t need to divide by 18.)

Divide that number by your ketone level number.

So, essentially: (Glucose Level / 18) / Ketone Level = Glucose Ketone Index

Now you have your glucose ketone index!

What Affects Your GKI?

Many lifestyle and environmental factors can affect your GKI because both ketone and glucose levels change easily in response to diet, exercise, stress and environmental conditions. If you’re trying to maintain a low GKI number, keep these habits in mind:

  • Fasting: After eating, it can be pretty tough to stay in a very low glucose-ketone range because there’s a degree of glucose increase. Practicing intermittent fasting can be beneficial for decreasing blood glucose levels, keeping GKI low and maintaining good health.
  • Nutrition: If your glucose levels are high, eating a ketogenic diet and watching out for hidden carbs can help improve that GKI ratio.
  • Stress: When we’re stressed, hormones like cortisol and epinephrine are released, causing blood sugar to rise. To keep that ratio low, focus on daily stress-reducing practices and try to get plenty of rest.

Dial In to Your Health: Measure Both Glucose and Ketone Levels

The GKI is a useful tool for finding your ideal keto macros so you can achieve optimal health. While ketone testing is useful for knowing if you’re in ketosis or not, the GKI takes it one step further by taking in account your glucose levels as well.

How should you use these numbers? That’s entirely up to you, but most people use it to dial in their nutrition, track their progress in ketosis and recognize which foods helps them reach their health goals.

By carefully monitoring your GKI, you can more easily enter (and stay in) ketosis and reap all the benefits.


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Responses (22)

  1. 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.

  2. Hey Dan, it’s not completely necessary but it’s a useful tool depending on what your goals are.

  3. 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!

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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!

  10. 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.

  11. 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.

  12. Hi can anyone tell me how long it took to show up ketones? i’m on day 5 of keto and nothing yet

  13. 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.

  14. 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.

  15. 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.

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