Diabetic Ketoacidosis — DKA

A blood glucose of 350 mg/dL with a pH of 7.2 and fruity breath tells you the body is burning fat for fuel — and the acid it produces can kill before the sugar does.

DKA occurs when absolute or relative insulin deficiency forces the body to break down fat for energy, producing ketone bodies (beta-hydroxybutyrate, acetoacetate, acetone) that overwhelm buffering capacity and cause metabolic acidosis. Classic lab findings: blood glucose typically 250–600 mg/dL, arterial pH below 7.30, serum bicarbonate below 18 mEq/L, positive serum ketones, and an elevated anion gap. Clinical presentation includes Kussmaul respirations (deep, rapid breathing — the lungs compensating for acidosis), fruity acetone breath, polyuria, polydipsia, nausea/vomiting, abdominal pain, and altered mental status. Treatment priorities follow a specific sequence: aggressive IV fluid resuscitation first (0.9% NS initially to correct dehydration), then continuous IV regular insulin infusion (not subcutaneous, not rapid-acting analogs), and potassium replacement guided by serum levels — potassium must be at least 3.3 mEq/L before starting insulin, because insulin drives potassium intracellularly and can cause fatal hypokalemia. Monitor glucose hourly; when it drops to 250 mg/dL, switch IV fluids to D5 with half-normal saline to prevent hypoglycemia and cerebral edema while continuing the insulin drip until the anion gap closes.

Key Distinctions

Don't confuse DKA with HHS — DKA has significant acidosis and ketones with moderately elevated glucose; HHS has extreme hyperglycemia (often >600 mg/dL) with minimal ketosis and no significant acidosis. Students assume you correct glucose first, but fluids come first and potassium status determines when insulin can safely start. Kussmaul respirations are compensatory for metabolic acidosis, not a respiratory problem — do not treat with oxygen or bronchodilators.

Clinical Pearl

Fluids first, potassium second, insulin third. If K+ is below 3.3, giving insulin without replacing potassium can stop the heart before the acidosis does.