The main difference between these three types of ketosis is the level of ketones in your blood. With both nutritional ketosis and exogenous ketosis, blood BHB levels usually remain below 8 mM. By contrast, during diabetic ketoacidosis BHB levels in the blood are more than twice as high (over 20 mM).
Diabetic ketoacidosis usually only occurs in Type I diabetics who produce no insulin. Blood glucose rises very high but because there is no insulin released, glucose cannot enter the cells, and the body wrongly believes it is starving. This leads to uncontrolled ketone production and should be treated as a medical emergency.