When we are starting out on the keto diet, our bodies produce very low ketone levels. This is because the body does not require lots of ketones for energy. It prefers to use glucose which is produced from dietary carbohydrates. When we deprive the body of dietary carbohydrates, the body burns up all available and all stored glucose, and turns to turning fat into ketones for energy.
Ketosis is defined as Blood Ketones > 0.5mmol/L. This is the minimum level of ketones in the body when Nutritional Ketosis (or light ketosis) begins. The body is just starting out and learning to use ketones for energy.
When the body starts to produce ketones regularly in the absence of glucose, the ketones level in the blood will rise. When the ketone levels are between 1.5mmol/L and 3.0mmol/L, it is considered in Optimum Ketosis. This is the usual maintenance ketosis level which most people will remain unless they are doing Intermittent Fasting.
When we do Intermittent Fasting with the intention of losing body weight in fats, we tend to increase the amount of ketones in the blood, and it will usually be between 3.0mmol/L and 5.0mmol/L. This is listed as Starvation Ketosis (fasting ketosis), not because the body is starving, but because the body thinks it is starving and starts to actively turn stored fats into ketones for energy.
The body system of a healthy non-diabetic person will maintain it’s own equilibrium of blood glucose and blood ketones, and will rarely exceed 5.0mmol/L in blood ketones.