Summary
Ketosis is a metabolic state where ketones and FFA replace glucose as the primary fuel of
the body in most tissues. The presence of ketosis indicates that fat breakdown has been
activated in the body and that the entire pathway of fat degradation is intact. The lack of ketosis
in states such as fasting and a ketogenic diet known to induce ketosis would indicate the presence
of a metabolic abnormality.
Ketosis can be delineated into ketonemia, the presence of ketones in the bloodstream, and
ketonuria, the presence of ketones in the urine. Clinically, ketosis is defined as a ketone
concentration of 0.2 mmol. A ketogenic diet or fasting will result in ketone levels between 4 and 8
mmol. Ketoacidosis is defined as 8 mmol or higher and pathological ketoacidosis, as in diabetic
ketoacidosis, can result in ketone concentrations of 20 mmol or greater. Ketoacidosis, as it
occurs in Type I diabetics and alcoholics and which is potentially fatal, will not occur in non-
diabetic individuals due to built in feedback loops whereby excess ketones stimulate the release of
insulin, slowing ketone body formation.
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