Urine and Serum Ketone Testing

Insulin does more than lower blood glucose. It suppresses lipolysis, the breakdown of stored fat. When effective insulin is absent or markedly insufficient, cells cannot use glucose adequately and the liver shifts toward fatty-acid oxidation. This produces ketones: beta-hydroxybutyrate (β-HB), acetoacetate, and acetone. Ketones can be used as an alternative fuel for a limited time. In diabetic ketoacidosis (DKA), however, production outpaces clearance. β-HB predominates, and its accumulation contributes to high-anion-gap metabolic acidosis. The patient becomes dehydrated from osmotic diuresis, then progressively acidemic as ketones rise. Ketones are a warning signal, not a diagnosis by themselves. Fasting, prolonged vomiting, alcohol use, and very-low-carbohydrate intake can also produce ketosis. DKA becomes more likely when ketones occur with diabetes, insulin interruption, hyperglycemia or SGLT2-inhibitor use, dehydration, abdominal symptoms, deep respirations, or altered mental status.