About the Glucose Ketone Index Calculator
The glucose ketone index (GKI) is a single number that combines your blood glucose and blood ketone (beta-hydroxybutyrate) readings. It was proposed by Meidenbauer, Mukherjee and Seyfried in 2015 as a way to track metabolic state on ketogenic diets and fasting: the lower the GKI, the more your metabolism is running on ketones rather than glucose. The paper suggests a “zone of metabolic management” at a GKI of about 1–2 in humans, with values approaching 1.0 considered most therapeutic.
Enter a glucose reading in mg/dL (US) or mmol/L (most other countries) and a blood ketone reading in mmol/L, ideally taken at the same time from a dual meter. The calculator converts glucose to mmol/L, divides by ketones and shows which band you fall into. It is used by keto dieters, people doing extended fasts and those following a clinician-supervised therapeutic ketogenic diet.
Breath and urine ketone readings cannot be used — GKI needs a blood BHB value. Readings vary through the day, so test at a consistent time (for example 2–3 hours after a meal or first thing in the morning). The wider bands shown here (3–6, 6–9, above 9) are conventions from the ketogenic-diet community, not thresholds from the original paper or any medical body, and they are not diagnostic. In people with diabetes, high ketones can signal diabetic ketoacidosis (the 2024 ADA/EASD consensus uses beta-hydroxybutyrate of 3.0 mmol/L or more with glucose of 200 mg/dL or more, or known diabetes).
With the default inputs, the glucose ketone index is 3.15. Change any value above to recalculate instantly.
How to use the glucose ketone index calculator
- 1Measure blood glucose and blood ketones at the same time, ideally with a dual meter.
- 2Choose the glucose unit your meter uses (mg/dL or mmol/L).
- 3Enter both readings.
- 4Read your GKI and ketosis band, and track it at the same time of day over several days.
Formula and method
Both readings must be in the same unit, millimoles per litre, before dividing. Glucose in mg/dL is converted using the molecular weight of glucose (180.16 g/mol), which gives the factor 18.016 used in the original GKI paper. Blood beta-hydroxybutyrate meters already report in mmol/L.
Meidenbauer, Mukherjee and Seyfried (2015) proposed GKI values of about 1–2 as the zone of metabolic management, with values approaching 1.0 as potentially most therapeutic. The wider bands used here are community conventions rather than clinical thresholds: above 9 not in ketosis, 6–9 low ketosis (typical for weight loss), 3–6 moderate ketosis, 1–3 high therapeutic ketosis, and below 1 the highest level. The calculator also shows the ketone level you would need for a GKI of 3 at your current glucose.
- GKI
- Glucose ketone index (unitless)
- Glucose
- Blood glucose, converted to mmol/L
- Ketones
- Blood beta-hydroxybutyrate in mmol/L
Worked examples
Glucose 85 mg/dL, ketones 1.5 mmol/L
85 ÷ 18.016 = 4.72 mmol/L glucose. Dividing by 1.5 mmol/L ketones gives a GKI of about 3.1 — moderate ketosis, just above the therapeutic range.
mmol/L meter during a fast
With glucose already in mmol/L, the GKI is 4.2 ÷ 3.5 = 1.2, which falls in the high therapeutic band typical of extended fasting.
Starting keto: glucose 100 mg/dL, ketones 0.4
100 mg/dL is 5.55 mmol/L; divided by 0.4 that is a GKI of about 13.9, so you are not yet in ketosis. To reach a GKI of 3 at this glucose you would need ketones of about 1.85 mmol/L.
Frequently asked questions
What is a good GKI number?+
For general ketogenic dieting and weight loss, a GKI between about 6 and 9 is typical. Values of 3–6 indicate moderate ketosis, and 1–3 is the range often targeted in clinician-supervised therapeutic ketogenic diets.
How do I convert glucose mg/dL to mmol/L for GKI?+
Divide mg/dL by 18 (more precisely 18.016). For example, 90 mg/dL is about 5.0 mmol/L. This calculator does the conversion automatically when you choose mg/dL.
Can I use urine or breath ketones for GKI?+
No. GKI is defined using blood beta-hydroxybutyrate in mmol/L. Urine strips measure acetoacetate and breath meters measure acetone, which do not convert reliably to blood BHB.
When is the best time to test GKI?+
Test at a consistent time, such as in the morning before eating or two to three hours after a meal. Glucose and ketones both move during the day, so consistent timing makes trends meaningful.
Is a very low GKI dangerous?+
In people without diabetes, a low GKI from fasting or keto is usually nutritional ketosis. In people with diabetes, blood ketones of 3.0 mmol/L or more can mean diabetic ketoacidosis — a medical emergency — and about 10% of cases occur with glucose below 200 mg/dL (euglycaemic DKA), especially with SGLT2 inhibitors.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.