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, 2

  • However, this threshold has been de-emphasized in recent guidelines due to increasing incidence of euglycemic DKA, particularly in patients on SGLT2 inhibitors 3, 2, 4
  • Euglycemic DKA (glucose <250 mg/dL with ketoacidosis) is increasingly common and should not be dismissed 3

• Metabolic Acidosis:

  • Venous pH <7.3 1, 2
  • Serum bicarbonate <15 mEq/L 1, 2
  • Anion gap >10-12 mEq/L (calculated as [Na⁺] - ([Cl⁻] + [HCO₃⁻])) 1, 2

• Ketosis:

  • Elevated blood β-hydroxybutyrate (β-OHB) - this is the preferred measurement 1, 3, 2
  • Moderate ketonuria or ketonemia 1

Severity Classification

DKA severity determines monitoring intensity and prognosis 2:

• 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 1, 3, 2:

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

Additional tests to consider based on clinical presentation 4:

• Bacterial cultures (blood, urine, throat) if infection suspected 1
• Amylase, lipase, hepatic transaminases, troponin, creatine kinase 4
• Chest radiography 4

Critical Ketone Measurement Considerations

Direct blood β-hydroxybutyrate (β-OHB) measurement is mandatory - do NOT rely on urine ketones or nitroprusside-based tests. 1, 3, 2

The nitroprusside method only measures acetoacetate and acetone, completely missing β-OHB, which is 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. Point-of-care β-OHB testing at triage has 98% sensitivity and 85% specificity for DKA diagnosis 5.

Common Diagnostic Pitfalls to Avoid

• Never dismiss DKA because glucose is <250 mg/dL - euglycemic DKA is increasingly common, especially with SGLT2 inhibitors 3, 2, 4

• Never rely solely on urine ketones for diagnosis or monitoring, as they miss β-OHB and can be falsely negative early in DKA 1, 3

• Do not repeat arterial blood gases unnecessarily - after initial diagnosis, venous pH and anion gap adequately monitor acidosis resolution (venous pH typically 0.03 units lower than arterial) 1

• Recognize diabetic ketoalkalosis - 23% of DKA cases present with pH >7.4 due to concurrent metabolic alkalosis or respiratory alkalosis, yet still have severe ketoacidosis requiring full DKA treatment 6

Resolution Criteria

DKA is resolved when ALL of the following are met 1, 3, 2:

• 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 1, 3, 2:

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