Urine and Serum Ketone Testing

Insulin normally allows glucose to move from the bloodstream into cells for energy. When insulin is absent or insufficient, cells cannot use available glucose effectively and the body switches to fat breakdown. The liver converts fatty acids into ketones: beta-hydroxybutyrate (β-HB), acetoacetate, and acetone. Ketones can serve as an alternative fuel during fasting. In diabetes, however, a large or rapidly rising ketone level may signal severe insulin deficiency. β-HB is the predominant ketone in diabetic ketoacidosis (DKA), and its accumulation contributes to metabolic acidosis. Ketosis is not automatically DKA. A person who has eaten poorly may have small ketones without severe hyperglycemia or acidosis. DKA involves clinically significant ketonemia plus metabolic acidosis and can progress to dehydration, potassium disturbances, shock, and altered mental status. A positive urine strip is therefore a warning sign, not a diagnosis by itself. SGLT2 inhibitors create an important exception to the usual pattern. These medications increase urinary glucose loss, so a patient can develop dangerous ketosis with glucose that is less elevated than expected. Symptoms and ketones matter even when the glucose value does not...