nonketotic

Nonketotic is an adjective used in medical contexts to describe a state in which ketone bodies are absent or present at low levels. The term is most often encountered in two distinct areas: metabolic disorders associated with hyperglycemia and the rare inherited metabolic condition known as nonketotic hyperglycinemia.

Nonketotic hyperglycemia refers to severe hyperglycemia with minimal ketosis. It is most commonly described in hyperosmolar hyperglycemic state (HHS), typically occurring in older adults with type 2 diabetes. In nonketotic states, insulin is insufficient to promote glucose uptake but sufficient to inhibit significant ketogenesis, so ketone production remains low. Patients present with marked hyperglycemia, dehydration, and mental status changes due to hyperosmolarity; ketoacids are not elevated. Management centers on aggressive IV fluids, electrolyte correction, and insulin therapy, with attention to triggers such as infection.

Nonketotic hyperglycinemia is a separate, rare autosomal recessive disorder caused by defects in the glycine cleavage system, leading to elevated glycine levels in blood and cerebrospinal fluid. It is also called glycine encephalopathy. Onset ranges from neonatal to late infancy, with hypotonia, lethargy, seizures, and progressive encephalopathy. Diagnosis relies on CSF and plasma glycine measurements and the CSF-to-plasma glycine ratio. Treatment is supportive and multidisciplinary; prognosis is generally poor, though management has improved in some cases.

Because ketosis is a key feature distinguishing certain metabolic states, the label nonketotic is used to separate these conditions from ketoacidosis-driven states such as diabetic ketoacidosis. In other contexts, the term may appear as part of the formal name of a disorder (for example, nonketotic hyperglycinemia).