What are the diagnostic criteria for diabetic ketoacidosis (DKA) in a patient with diabetes?

Diagnostic Criteria for Diabetic Ketoacidosis (DKA)

The diagnosis of DKA requires three simultaneous components: blood glucose >250 mg/dL (or prior diabetes history), venous pH <7.3, serum bicarbonate <15 mEq/L, and elevated blood β-hydroxybutyrate. 1

Core Diagnostic Triad

DKA diagnosis mandates all three of the following criteria be present simultaneously: 2

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

The anion gap should be >10-12 mEq/L, calculated as [Na⁺] - ([Cl⁻] + [HCO₃⁻]). 1, 4

Critical Measurement: β-Hydroxybutyrate

Direct blood measurement of β-hydroxybutyrate is the preferred and required method for diagnosing DKA—never rely on urine ketones or nitroprusside-based tests. 1, 2

The nitroprusside method only detects acetoacetate and acetone, completely missing β-OHB, which is the predominant and strongest ketoacid in DKA. 1, 2 During treatment, β-OHB converts to acetoacetate, paradoxically making nitroprusside tests appear worse even as the patient improves. 1

Severity Classification

Once DKA is diagnosed, classify severity based on pH and bicarbonate: 1

• 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 1, 2
• Severe DKA: pH <7.00, bicarbonate <10 mEq/L, stuporous or comatose 1, 2

Severe DKA carries higher morbidity and mortality and often requires intensive monitoring including central venous and intra-arterial pressure monitoring. 1

Essential Initial Laboratory Workup

Obtain immediately upon presentation: 1, 2

• Complete metabolic panel (electrolytes, BUN, creatinine)
• Venous blood gas (pH, bicarbonate)
• Blood β-hydroxybutyrate (not urine ketones)
• Complete blood count
• Urinalysis
• Serum osmolality
• Electrocardiogram
• Calculate anion gap and corrected sodium

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

If infection is suspected, obtain bacterial cultures of urine, blood, and throat. 1

Euglycemic DKA: Critical Exception

Approximately 10% of DKA cases present with euglycemic DKA (glucose <200 mg/dL), making hyperglycemia no longer an absolute requirement for diagnosis. 5

Euglycemic DKA is increasingly common and associated with: 5, 2

• SGLT2 inhibitor therapy (most common cause)
• Pregnancy
• Reduced food intake/starvation
• Alcohol use
• Chronic liver disease
• Glycogen storage disorders

Never dismiss DKA possibility because glucose is <250 mg/dL—the acidosis and ketosis criteria remain mandatory regardless of glucose level. 2

Resolution Criteria

DKA is considered resolved only when ALL of the following are met: 1, 5, 2

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

Common Diagnostic Pitfalls to Avoid

• Never use urine ketones or nitroprusside methods for diagnosis or monitoring—they miss β-OHB and provide falsely reassuring or misleading results. 1, 2
• Do not rely solely on glucose levels—ketoacidosis takes longer to resolve than hyperglycemia, and premature insulin cessation based on normalized glucose causes recurrence. 5
• Avoid repeating arterial blood gases unnecessarily—after initial diagnosis, venous pH (typically 0.03 units lower than arterial) adequately monitors acidosis resolution. 1
• Do not dismiss DKA in type 2 diabetes—although less common, it occurs with the same diagnostic criteria and requires identical management. 2