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

Diagnostic Criteria for Diabetic Ketoacidosis (DKA)

DKA is diagnosed when all three core criteria 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 components must be present together for DKA diagnosis:

• Hyperglycemia: Blood glucose >250 mg/dL 1, 2

  • However, this threshold has been de-emphasized in recent guidelines due to increasing incidence of euglycemic DKA, particularly in patients on SGLT2 inhibitors 2, 3
  • Do not dismiss DKA if glucose is <250 mg/dL—euglycemic DKA is increasingly common 4

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

  • Direct blood β-OHB measurement is the gold standard—NOT urine ketones or nitroprusside-based tests 1, 4

Severity Classification

DKA severity determines monitoring intensity and prognosis based on pH, bicarbonate, and mental status 2:

• 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 1, 2:

• Complete metabolic panel including sodium, potassium, chloride, bicarbonate, BUN, creatinine, and glucose 2
• Venous blood gas for pH, pCO2, and bicarbonate 2
• Blood β-hydroxybutyrate (not urine ketones) 2, 4
• Complete blood count with differential 2
• Urinalysis 2
• Serum osmolality 2
• Electrocardiogram 2
• Bacterial cultures of urine, blood, and throat if infection is suspected 1

Calculate corrected sodium using: [measured Na (mEq/L)] + [glucose (mg/dL) - 100]/100 × 1.6 1

Critical Pitfalls to Avoid

• Never rely on urine ketones or nitroprusside-based tests for diagnosis or monitoring 1, 4

  • The nitroprusside method only measures acetoacetate and acetone, completely missing β-OHB—the predominant and strongest ketoacid in DKA 1, 4
  • During treatment, β-OHB converts to acetoacetate, making nitroprusside tests paradoxically appear worse even as the patient improves 1

• Do not dismiss DKA because glucose is <250 mg/dL 4, 3

  • SGLT2 inhibitors significantly increase risk of euglycemic DKA in both type 1 and type 2 diabetes 2, 4

• After initial arterial blood gas, use venous pH for monitoring 1

  • Venous pH is typically 0.03 units lower than arterial and adequately monitors acidosis resolution without repeated arterial sticks 1

Monitoring During Treatment

Draw blood every 2-4 hours to measure 1, 2:

• Electrolytes (especially potassium)
• Glucose
• Venous pH
• β-hydroxybutyrate
• Anion gap
• BUN/creatinine
• Serum osmolality

Resolution Criteria

DKA is resolved when ALL of the following are met 2, 4:

• Glucose <200 mg/dL 1, 2
• Venous pH >7.3 1, 2
• Serum bicarbonate ≥18 mEq/L 1, 2
• Anion gap ≤12 mEq/L 2, 4

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