Nutritional ketosis is defined as achieving and sustaining a blood ketone level above 0.5 millimolar, ideally between 1 and 3 millimolar.

“So nutritional ketosis could be, it's defined...they, kind of, have the same definition in my mind. It's achieving and sustaining a level of blood ketones. And I think when people say they've done the ketogenic diet, they did that it didn't work for them or it did work for them, I would ask the question, "Well, did you measure blood ketones? Did you confirm, in fact, that you were able to achieve a state of ketosis?" Defined as an elevation of blood ketones above 0.5 millimolar at the very least. Ideally, you want to stay between one and three millimolar of ketones.”