What are the diagnostic criteria for diabetic ketoacidosis (DKA)?

Diagnostic Criteria for Diabetic Ketoacidosis (DKA)

DKA is diagnosed when all three components are present simultaneously: blood glucose >250 mg/dL, venous pH <7.3 with serum bicarbonate <15 mEq/L, and elevated blood β-hydroxybutyrate (β-OHB). 1, 2

Core Diagnostic Triad

All three criteria must be met for DKA diagnosis:

• Hyperglycemia: Blood glucose >250 mg/dL 3, 1, 2
• Metabolic acidosis: Venous pH <7.3 AND serum bicarbonate <15 mEq/L 3, 1, 2
• Ketosis: Elevated blood ketones, preferably measured as β-hydroxybutyrate 1, 2

The anion gap should be >10-12 mEq/L, calculated as [Na⁺] - ([Cl⁻] + [HCO₃⁻]). 1, 2

Severity Classification

DKA severity determines monitoring intensity and prognosis:

• Mild DKA: pH 7.25-7.30, bicarbonate 15-18 mEq/L, alert mental status 1, 2
• Moderate DKA: pH 7.00-7.24, bicarbonate 10-15 mEq/L, drowsy/lethargic mental status 1, 2
• Severe DKA: pH <7.00, bicarbonate <10 mEq/L, stuporous or comatose mental status, associated with higher morbidity and mortality 1, 2

Essential Laboratory Workup

Obtain immediately upon presentation:

• Complete metabolic panel (sodium, potassium, chloride, bicarbonate, BUN, creatinine, glucose) 1, 2
• Venous blood gas (pH, pCO₂, bicarbonate) 1, 2
• Blood β-hydroxybutyrate measurement (gold standard for ketone assessment) 1, 2
• Complete blood count with differential 3, 1
• Urinalysis 3, 1
• Serum osmolality 3, 1
• Electrocardiogram 1, 2
• HbA1c to distinguish acute versus chronic poor control 3
• Bacterial cultures (blood, urine, throat) if infection suspected 3, 1

Critical Ketone Measurement Considerations

Use direct blood β-hydroxybutyrate measurement, NOT urine ketones or nitroprusside-based tests. 1, 2, 4

The nitroprusside method (used in urine dipsticks and some serum tests) only measures acetoacetate and acetone, completely missing β-hydroxybutyrate—the predominant and strongest ketoacid in DKA. 1, 2 During treatment, β-hydroxybutyrate is converted to acetoacetate, which paradoxically makes nitroprusside tests appear worse even as the patient improves. 1

Important Caveat: Euglycemic DKA

The hyperglycemia threshold (>250 mg/dL) has been de-emphasized in recent guidelines due to increasing incidence of euglycemic DKA. 2, 5

Euglycemic DKA (glucose <250 mg/dL with ketoacidosis) occurs in:

• Patients on SGLT2 inhibitors 2, 4, 5
• Recent insulin use 6
• Decreased caloric intake or starvation 6
• Heavy alcohol consumption 6
• Pregnancy 6

Do not dismiss DKA possibility because glucose is <250 mg/dL, especially in patients on SGLT2 inhibitors. 4

Differential Diagnosis

DKA must be distinguished from other causes of high anion gap metabolic acidosis:

• Lactic acidosis: Measure blood lactate 2
• Toxic ingestions: Salicylate, methanol, ethylene glycol 3, 2
• Alcoholic ketoacidosis: Clinical history, glucose typically mildly elevated or low 3
• Starvation ketosis: Bicarbonate usually not lower than 18 mEq/L 3
• Chronic renal failure: Typically hyperchloremic acidosis rather than high anion gap 3

Resolution Criteria

DKA is resolved when ALL of the following are met:

• Glucose <200 mg/dL 1, 2
• Venous pH >7.3 1, 2
• Serum bicarbonate ≥18 mEq/L 1, 2
• Anion gap ≤12 mEq/L 1, 2

Ketonemia typically takes longer to clear than hyperglycemia, requiring continued monitoring and insulin therapy even after glucose normalizes. 1, 2

Monitoring During Treatment

Draw blood every 2-4 hours to measure:

• Electrolytes (sodium, potassium, chloride, bicarbonate) 1, 2
• Glucose 1, 2
• Venous pH 1, 2
• β-hydroxybutyrate 1, 2
• Anion gap 1, 2
• BUN/creatinine 1, 2
• Serum osmolality 1, 2

After initial diagnosis, repeat arterial blood gases are generally unnecessary—venous pH and anion gap adequately monitor acidosis resolution, with venous pH typically 0.03 units lower than arterial. 1