The Glucose Ketone Index (GKI) serves as a single, powerful metric for assessing an individual’s metabolic state, moving beyond the limitations of measuring blood sugar or ketones in isolation. This index is a ratio that summarizes the balance between the body’s primary fuel sources—glucose and ketone bodies—providing insight into metabolic flexibility. By integrating both readings, the GKI helps determine how effectively the body is utilizing fat for energy, which is a state known as ketosis. A lower GKI number generally correlates with a deeper state of ketosis, which is a goal for those seeking therapeutic benefits or improved metabolic health.
The Two Measurements Required
Determining the GKI requires two precise measurements taken from a small blood sample: blood glucose and blood ketones. These readings offer a real-time snapshot of the body’s energy environment, which is constantly shifting based on diet, activity, and fasting status. Blood glucose, commonly measured in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L), represents the body’s immediate and readily available fuel source derived from carbohydrates.
The second necessary measurement is the concentration of blood ketones, specifically beta-hydroxybutyrate (BHB), which is the most abundant ketone body in the bloodstream during ketosis. Ketones are an alternative fuel source produced by the liver when carbohydrate intake is low and fat breakdown is increased. This reading, typically measured in mmol/L, indicates the extent to which the body has shifted away from burning glucose toward burning fat for fuel.
Calculating the Glucose Ketone Index
The calculation of the GKI is a simple division, but it requires a necessary conversion to ensure both measurements are in the same unit of measure. The GKI is determined by dividing the blood glucose concentration by the blood ketone concentration. Both values must be in millimoles per liter (mmol/L) for the ratio to be accurate.
Since many glucose meters in the United States display results in milligrams per deciliter (mg/dL), this glucose reading must first be divided by 18 to convert it to mmol/L. For example, if your glucose reading is 90 mg/dL, dividing it by 18 yields 5.0 mmol/L. The simplest formula for those using mg/dL for glucose is: (Glucose in mg/dL ÷ 18) ÷ Ketones in mmol/L = GKI.
If your glucose meter already provides the reading in mmol/L, the calculation is more straightforward, involving only the division of the two measurements. You simply divide the glucose value in mmol/L by the ketone value in mmol/L to get the final GKI. It is best practice to take both readings at the same time of day, ideally while in a fasted state or two to three hours after a meal, to ensure consistency in tracking your metabolic trend.
What Your GKI Values Mean
The numerical value of your GKI offers a clear interpretation of your current metabolic state, with a lower number indicating a greater reliance on fat as fuel. A GKI value greater than 9.0 suggests the body is primarily in a sugar-burning state and has not entered ketosis. This range is typical for individuals consuming a standard, high-carbohydrate diet.
A GKI between 6.0 and 9.0 is considered mild or low-level ketosis, which is a common target for those aiming for general wellness or modest weight loss. Moving deeper, a GKI between 3.0 and 6.0 signifies moderate ketosis and is often targeted by individuals managing metabolic conditions like type 2 diabetes or insulin resistance. This range suggests a more consistent use of fat for energy.
The most profound level of fat adaptation is reflected by a GKI between 1.0 and 3.0, known as deep therapeutic ketosis. This state is often pursued under medical supervision for managing certain neurological conditions, such as epilepsy, or as an adjunct therapy for some forms of cancer. Values below 1.0 represent the highest degree of therapeutic ketosis, which requires extremely strict dietary adherence and often prolonged fasting periods.
Why Track the Glucose Ketone Index (GKI)
Tracking the GKI provides a comprehensive method for evaluating metabolic flexibility, which is the body’s ability to seamlessly switch between burning glucose and burning fat for fuel. The GKI combines both metrics into one actionable number, reflecting the true metabolic environment, unlike relying solely on ketone levels which can be misleading if glucose is also high.
For those following a ketogenic or very low-carbohydrate diet, monitoring the GKI is an objective way to confirm dietary compliance and optimize the depth of ketosis. A consistently low GKI confirms that dietary choices and lifestyle factors, such as exercise and fasting, are effectively promoting fat adaptation. Furthermore, the GKI has significant value in therapeutic settings, as its original use was to monitor the metabolic state in protocols for conditions like brain cancer, where low glucose availability is a specific goal.