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 1, 3, 2

  • Note: This threshold has been de-emphasized due to increasing euglycemic DKA, particularly with SGLT2 inhibitor use 3, 4
  • Euglycemic DKA (glucose <250 mg/dL with ketoacidosis) is increasingly common and should not exclude the diagnosis 3

• Metabolic Acidosis: Venous pH <7.3 AND serum bicarbonate <15 mEq/L 1, 3, 2

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

• Ketosis: Elevated blood ketones, preferably measured as β-hydroxybutyrate 1, 3, 2

  • Direct blood β-OHB measurement is the gold standard 1, 3, 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, 3, 2

• Moderate DKA: pH 7.00-7.24, bicarbonate 10-15 mEq/L, drowsy/lethargic mental status 1, 3, 2

• Severe DKA: pH <7.00, bicarbonate <10 mEq/L, stuporous or comatose mental status, associated with higher morbidity and mortality 1, 3, 2

Essential Laboratory Workup

Obtain immediately upon presentation:

• Complete metabolic panel (sodium, potassium, chloride, bicarbonate, BUN, creatinine, glucose) 1, 3, 2
• Venous blood gas (pH, pCO2, bicarbonate) 1, 3, 2
• Blood β-hydroxybutyrate (β-OHB) - preferred ketone measurement 1, 3, 2
• Complete blood count with differential 1, 3, 2
• Urinalysis 1, 3, 2
• Serum osmolality 3, 2
• Electrocardiogram 3, 2
• Calculate anion gap 1, 2
• Correct serum sodium for hyperglycemia: [measured Na (mEq/L)] + [glucose (mg/dL) - 100]/100 × 1.6 1

Additional tests to consider based on clinical presentation:

• Bacterial cultures (blood, urine, throat) if infection suspected 1
• Amylase/lipase if abdominal pain present 4
• Troponin, creatine kinase if cardiac symptoms 4
• Chest radiography if respiratory symptoms 4

Critical Ketone Measurement Considerations

Never rely on urine ketones or nitroprusside-based tests for diagnosis or monitoring. 1, 3, 2

• The nitroprusside method only measures acetoacetate and acetone, completely missing β-OHB—the predominant and strongest ketoacid in DKA 1, 3
• During treatment, β-OHB is converted to acetoacetate, which paradoxically makes nitroprusside tests appear worse even as the patient improves 1
• Blood β-OHB measurement is superior for both diagnosis and monitoring 1, 3, 2

Resolution Criteria

DKA is resolved when ALL of the following are met:

• Glucose <200 mg/dL 1, 2
• Venous pH >7.3 1, 3, 2
• Serum bicarbonate ≥18 mEq/L 1, 3, 2
• Anion gap ≤12 mEq/L 1, 3, 2

Common Diagnostic Pitfalls to Avoid

• Do not dismiss DKA because glucose is <250 mg/dL - euglycemic DKA is increasingly common, especially with SGLT2 inhibitors 3, 4
• Do not use urine ketones for diagnosis - they miss β-OHB and can be falsely negative early in DKA 1, 3
• Do not rely solely on arterial blood gases - venous pH (typically 0.03 units lower than arterial) is adequate for diagnosis and monitoring 1
• Do not stop monitoring ketones prematurely - ketonemia takes longer to clear than hyperglycemia 1, 2

Monitoring During Treatment

Draw blood every 2-4 hours to measure:

• Electrolytes (sodium, potassium, chloride) 1, 3, 2
• Glucose 1, 3, 2
• Venous pH 1, 3, 2
• β-hydroxybutyrate 1, 3
• Anion gap 1, 3, 2
• BUN, creatinine 1, 3, 2
• Serum osmolality 1, 3, 2