Diagnostic Criteria for Diabetic Ketoacidosis (DKA)
DKA is diagnosed when all three of the following criteria are present simultaneously: 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
The diagnosis requires three components present at the same time 2:
- Hyperglycemia: Blood glucose >250 mg/dL 1
- Metabolic acidosis: Venous pH <7.3 AND serum bicarbonate <15 mEq/L 1
- Ketosis: Elevated blood ketones, measured as β-hydroxybutyrate 1, 2
Severity Classification
Once DKA is confirmed, classify severity based on pH and bicarbonate 1:
- Mild DKA: Venous pH 7.25-7.30, bicarbonate 15-18 mEq/L, alert mental status 1
- Moderate DKA: Venous pH 7.00-7.24, bicarbonate 10-15 mEq/L, drowsy/lethargic 1
- Severe DKA: Venous pH <7.00, bicarbonate <10 mEq/L, stuporous or comatose 1
Essential Laboratory Workup
Obtain immediately upon presentation 1:
- Complete metabolic panel (includes glucose, electrolytes, BUN, creatinine)
- Venous blood gas (for pH)
- Blood β-hydroxybutyrate (preferred ketone measurement)
- Complete blood count
- Urinalysis
- Serum osmolality
- Electrocardiogram
- Calculate anion gap: [Na⁺] - ([Cl⁻] + [HCO₃⁻]), which should be >10-12 mEq/L in DKA 1
If infection is suspected, obtain bacterial cultures of urine, blood, and throat 1.
Critical Ketone Measurement Considerations
Direct blood β-hydroxybutyrate (β-OHB) measurement is mandatory—do NOT rely on urine ketones or nitroprusside-based tests. 1, 2 The nitroprusside method only measures acetoacetate and acetone, completely missing β-OHB, which is the predominant and strongest ketoacid in DKA 1. During treatment, β-OHB converts to acetoacetate, which paradoxically makes nitroprusside tests appear worse even as the patient improves 1.
Euglycemic DKA: Important Exception
Approximately 10% of DKA cases present with euglycemic DKA (glucose <200 mg/dL) 3. In these cases, the diagnosis still requires venous pH <7.3, serum bicarbonate <15 mEq/L, and elevated blood ketones, but hyperglycemia may be absent 3, 2.
Risk factors for euglycemic DKA include 3:
- SGLT2 inhibitor therapy (most common cause)
- Pregnancy
- Reduced food intake/starvation
- Alcohol use
- Chronic liver disease
Do not dismiss DKA possibility because glucose is <250 mg/dL, especially in patients on SGLT2 inhibitors. 2
Resolution Criteria
DKA is considered resolved when ALL of the following are met 1, 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 rely on urine ketones for diagnosis or monitoring—they miss β-OHB and can be falsely negative early in DKA 1, 2
- Do not use arterial blood gases after initial diagnosis—venous pH (typically 0.03 units lower than arterial) adequately monitors acidosis resolution and avoids unnecessary arterial sticks 1
- Do not stop insulin therapy based on glucose levels alone—continue insulin until ketoacidosis resolves, as ketonemia takes longer to clear than hyperglycemia 1, 3
- Do not correct serum sodium without accounting for hyperglycemia—use the formula: [measured Na (mEq/L)] + [glucose (mg/dL) - 100]/100 × 1.6 1