What is the Glucose Ketone Index?
The Glucose Ketone Index (GKI) combines two finger-prick readings into a single number: how much sugar is in your blood compared with how many ketones are in your blood. Ketones are the fuel your liver makes from fat when insulin is low, such as overnight, during a fast, or on a low-carb diet. So the GKI is a quick way to see how much your body is running on fat rather than sugar at that moment.
A lower number means more ketones relative to glucose. A higher number means your body is mostly running on glucose, which is completely normal for anyone eating carbohydrates.
The index was described by researchers Joshua Meidenbauer, Purna Mukherjee and Thomas Seyfried in 2015, originally as a way to track metabolic therapy in clinical research. It has since become popular with people who follow keto diets or fasting.
The formula
If your meter shows glucose in mg/dL, it's divided by 18.016 first to convert it to mmol/L. This calculator does that for you.
Example: a fasted glucose of 5.0 mmol/L and ketones of 1.0 mmol/L gives a GKI of 5.0 — moderate ketosis. The same glucose with ketones of 0.2 gives a GKI of 25, which simply means you're not in ketosis.
How to get a reliable reading
First thing in the morning, before food or coffee, gives the most comparable numbers from day to day. Readings later in the day swing around with meals and activity.
A trace of fruit, juice or anything sweet on your finger can push glucose falsely high.
Glucose and ketones change through the day, so measure them within a few minutes of each other. Dual meters let you use one finger-prick for both.
A carb-heavy dinner or a late meal can noticeably change the next morning's numbers. The note field in the log is for exactly this.
Home meters can be off by 10–15%, and a single reading can be a fluke. A week or two of mornings tells you far more.
Frequently Asked Questions
No. Urine strips measure a different ketone (acetoacetate) that your body is getting rid of, and the result depends on how much water you've been drinking. They only give a rough colour band, not a blood level in mmol/L. They also become less reliable after a few weeks of low-carb eating. For a GKI you need a blood ketone meter that measures beta-hydroxybutyrate (BHB), used alongside a blood glucose reading.
Not at all. A GKI above 9 just means you're not in ketosis, which is where most people eating a normal diet sit most of the time. The GKI tells you about fuel use, not overall health. If you want to know about your general metabolic health, your fasting glucose, HbA1c and a GP check are more useful.
As a general guide used in Australia, a fasting glucose under about 5.5 mmol/L is considered normal. Between about 5.5 and 6.9 is a "grey zone" where a GP may suggest further testing. 7.0 or above on a lab test is in the diabetes range. A single home reading can't diagnose anything, so if your fasted readings are regularly above 5.5, it's worth mentioning to your GP.
"LO" usually means below the meter's measuring range, typically under 0.1 mmol/L. A GKI can't be calculated from zero, because you'd be dividing by nothing. You can enter 0.1 to get an approximate GKI, but the honest answer is simply "not in ketosis".
You can use it as a calculator, but please follow your diabetes team's advice on ketones rather than GKI zones. For people with diabetes, especially type 1 or anyone on SGLT2-inhibitor medicines, raised blood ketones can be a warning sign of diabetic ketoacidosis (DKA), which is a medical emergency. Ketone-lowering diets and fasting should be discussed with your doctor first, as medication doses may need adjusting.
iPhone: open this page in Safari, tap the Share button, then "Add to Home Screen". Android: open it in Chrome, tap the ⋮ menu, then "Add to Home screen" or "Install app". It will appear with its own GKI icon and open full-screen, like an app. Your log stays in that phone's browser.
Your log is saved automatically in this browser on this device. It isn't uploaded anywhere, so it won't appear on another phone or computer by itself. Use "Download backup" on one device and "Restore from file" on the other to move it across. Clearing your browser data will delete the log, so download a backup now and then.