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 Parameters
The diagnosis requires three components occurring together 2:
- Hyperglycemia: Blood glucose >250 mg/dL, though this threshold has been de-emphasized due to increasing incidence of euglycemic DKA, particularly in patients on SGLT2 inhibitors 2, 3
- Metabolic acidosis: Venous pH <7.3 AND serum bicarbonate <15 mEq/L 1, 2
- Ketosis: Elevated blood ketones, preferably measured as β-hydroxybutyrate 1, 2
The anion gap should be >10-12 mEq/L, calculated as [Na⁺] - ([Cl⁻] + [HCO₃⁻]) 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 with pH, pCO2, and bicarbonate 2
- Blood β-hydroxybutyrate measurement (gold standard) 2, 4
- Complete blood count with differential 2
- Urinalysis 1
- Serum osmolality 2
- Electrocardiogram 2
- Bacterial cultures (urine, blood, throat) if infection suspected 1
Critical Ketone Measurement Considerations
Never rely on urine ketones or nitroprusside-based tests for diagnosis or monitoring. 1, 2, 4 The nitroprusside method only measures acetoacetate and acetone, completely missing β-hydroxybutyrate—the predominant and strongest ketoacid in DKA 1, 4. During treatment, β-hydroxybutyrate converts to acetoacetate, paradoxically making nitroprusside tests appear worse even as the patient improves 1.
Direct blood β-hydroxybutyrate measurement is the preferred method for both diagnosis and monitoring 1, 2, 4, 5.
Severity Classification
DKA severity determines monitoring intensity and prognosis 2:
- Mild DKA: pH 7.25-7.30, bicarbonate 15-18 mEq/L, anion gap >10, alert mental status 1, 2
- Moderate DKA: pH 7.00-7.24, bicarbonate 10-15 mEq/L, anion gap >12, drowsy/lethargic mental status 1, 2
- Severe DKA: pH <7.00, bicarbonate <10 mEq/L, anion gap >12, stuporous or comatose mental status, associated with higher morbidity and mortality 1, 2
Special Considerations
Euglycemic DKA (glucose <250 mg/dL with ketoacidosis) is increasingly common, especially with SGLT2 inhibitors 2, 4, 3. Do not dismiss DKA possibility based on glucose <250 mg/dL alone 4.
Type 2 diabetes: Although less common, DKA can occur in type 2 diabetics and requires the same diagnostic approach 4. SGLT2 inhibitors significantly increase DKA risk in this population 4.
Monitoring During Treatment
Draw blood every 2-4 hours to measure 1, 2:
- Electrolytes, glucose, venous pH
- β-hydroxybutyrate
- Anion gap
- BUN, creatinine, serum osmolality
After initial diagnosis, repeat arterial blood gases are generally unnecessary—venous pH and anion gap adequately monitor acidosis resolution, with venous pH typically 0.03 units lower than arterial 1.
Resolution Criteria
DKA is resolved when ALL of the following are met 1, 2:
Ketonemia typically takes longer to clear than hyperglycemia, requiring continued monitoring and insulin therapy even after glucose normalizes 2.
Common Diagnostic Pitfalls to Avoid
- Never use urine ketones for diagnosis—they miss β-OHB and can be falsely negative early in DKA 1, 4
- Do not repeat arterial sticks unnecessarily—venous pH suffices for monitoring after initial diagnosis 1
- Do not dismiss DKA because glucose is <250 mg/dL—euglycemic DKA is increasingly common 4
- Correct serum sodium for hyperglycemia using: [measured Na (mEq/L)] + [glucose (mg/dL) - 100]/100 × 1.6 1