Ketone level

The image shows a comprehensive chart of different levels of ketosis, where blood ketone levels (mmol/L) change over time, with different fasting periods.

Important points

Baseline ketone level

It is between 0.0 – 0.5 mmol/L with a normal diet.

Fat burning starts

It starts after about 24 hours of fasting, when the ketone level reaches 1.0 mmol/L.

Optimal fat burning

After 36 hours of fasting, ketone levels are found at around 2.0 mmol/L; this is considered the optimal “ketone zone.”

Fast fat burning

After 48 hours of fasting, ketone levels rise to approximately 3.0 mmol/L, making fat burning more intense.

The diagram differentiates between the following types of ketosis:

Nutritional ketosis

Moderate ketone levels, typically between 0.5–3.0 mmol/L.

Post-workout ketosis

A similarly moderate, short-lived rise.

Starvation ketosis

It develops after prolonged fasting, with higher ketone levels.

Ketoacidosis

Rare in healthy people; can occur at dangerously high blood ketone levels (usually above 10 mmol/L), especially in cases of insulin deficiency .

The point

Fasting and carbohydrate deprivation increase blood ketone levels, which promotes fat burning , but is only safe up to a certain level.

Extremely high ketone levels can pose a health risk.