Ketones

Overview

Ketones measure the concentration of ketone bodies (acetoacetate, beta‑hydroxybutyrate, and acetone) in blood or urine, which are produced by the liver during fatty‑acid oxidation when glucose availability is low or insulin action is impaired. They serve as alternative energy substrates for the brain, heart, and skeletal muscle during fasting, prolonged exercise, or carbohydrate‑restricted diets. Elevated blood or urinary ketones (ketonemia/ketonuria) indicate states such as diabetic ketoacidosis, prolonged fasting, or very low‑carbohydrate diets, whereas very low levels are typical in fed states with normal glucose and insulin. Clinically, ketone testing is most important for early detection and monitoring of diabetic ketoacidosis and for guiding nutritional and metabolic management in diabetes and weight‑loss regimens.

Clinical Use Cases

  • Screening for and monitoring diabetic ketoacidosis in patients with type 1 or type 2 diabetes.
  • Evaluating unexplained nausea, vomiting, abdominal pain, or altered mental status in diabetic patients.
  • Assessing metabolic response to fasting, prolonged exercise, or ketogenic diets.
  • Supporting the workup of metabolic disorders that cause abnormal ketone production (e.g., inborn errors of metabolism).

Specimen Types

  • Serum or plasma (for beta‑hydroxybutyrate, the most clinically informative ketone).
  • Whole blood (finger‑prick test strips for point‑of‑care ketone measurement).
  • Urine (dipstick measurement of acetoacetate and, less commonly, ketones via semiquantitative tests).

Measurement Methods

  • Blood ketone meters using beta‑hydroxybutyrate‑specific test strips.
  • Laboratory enzymatic assay for beta‑hydroxybutyrate in serum or plasma.
  • Urinary ketone dipstick (nitroprusside‑based reaction detecting acetoacetate and, to a lesser extent, acetone).

Test Preparation and Influencing Factors

  • Fasting, ketotic diets, and intense exercise typically increase ketone levels.
  • In diabetic patients, insulin deficiency, infection, or stress‑induced hyperglycemia commonly trigger ketonuria/ketonemia.
  • Recent alcohol intake can raise ketones; certain medications (e.g., SGLT‑2 inhibitors) increase ketone formation even with near‑normal glucose.
  • Proper timing and storage of samples are important, as ketone bodies can volatilize or degrade in unpreserved specimens.

Synonyms

  • Ketone bodies.
  • Blood ketones / urine ketones.
  • Beta‑hydroxybutyrate (primary blood ketone measured in many assays).

Further Reading