Diagnostic Criteria for Diabetic Ketoacidosis (DKA)
DKA is diagnosed when all three core criteria are simultaneously present: blood glucose >250 mg/dL, venous pH <7.3, and serum bicarbonate <15 mEq/L, along with elevated blood ketones (preferably β-hydroxybutyrate). 1, 2
Core Diagnostic Triad
The American Diabetes Association requires all three components to be present concurrently for DKA diagnosis 2:
- Hyperglycemia: Blood glucose >250 mg/dL 1, 2
- Metabolic acidosis: Venous pH <7.3 1, 2
- Low bicarbonate: Serum bicarbonate <15 mEq/L 1, 2
- Ketonemia: Moderate ketonuria or ketonemia, preferably measured as blood β-hydroxybutyrate 1, 2
Essential Laboratory Workup
Upon presentation with suspected DKA, obtain the following immediately 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 (gold standard for ketone measurement, not urine ketones) 1, 2
- Anion gap calculation: [Na⁺] - ([Cl⁻] + [HCO₃⁻]), which should be >10-12 mEq/L in DKA 1, 2
- Complete blood count with differential 2
- Urinalysis 1
- Serum osmolality 2
- Electrocardiogram 2
Severity Classification
DKA severity determines monitoring intensity and prognosis 1, 2:
Mild DKA
- Venous pH: 7.25-7.30 1, 2
- Bicarbonate: 15-18 mEq/L 1, 2
- Anion gap: >10 mEq/L 2
- Mental status: Alert 1, 2
Moderate DKA
- Venous pH: 7.00-7.24 1, 2
- Bicarbonate: 10-15 mEq/L 1, 2
- Anion gap: >12 mEq/L 2
- Mental status: Drowsy/lethargic 1, 2
Severe DKA
- Venous pH: <7.00 1, 2
- Bicarbonate: <10 mEq/L 1, 2
- Anion gap: >12 mEq/L 2
- Mental status: Stuporous or comatose 1, 2
- Associated with higher morbidity and mortality, requiring intensive monitoring including potential central venous and intra-arterial pressure monitoring 1, 2
Critical Diagnostic Considerations
Euglycemic DKA
The glucose threshold of >250 mg/dL has been de-emphasized in recent guidelines due to increasing incidence of euglycemic DKA, particularly in patients on SGLT2 inhibitors 2, 3, 4. DKA can occur with blood glucose <200 mg/dL in these situations 3:
- Recent insulin use 3
- Decreased caloric intake 3
- Heavy alcohol consumption 3
- Pregnancy 3
- SGLT2 inhibitor use 2, 4
Ketone Measurement Pitfall
Direct blood measurement of β-hydroxybutyrate 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-hydroxybutyrate, which is the predominant ketoacid in DKA 1. During treatment, β-hydroxybutyrate converts to acetoacetate, paradoxically making nitroprusside tests appear worse even as the patient improves 1.
Corrected Sodium
Calculate corrected sodium for hyperglycemia using: [measured Na (mEq/L)] + [glucose (mg/dL) - 100]/100 × 1.6 1
Differential Diagnosis
DKA must be distinguished from other causes of high anion gap metabolic acidosis 2:
- Lactic acidosis: Measure blood lactate 1, 2
- Toxic ingestions: Salicylate, methanol, ethylene glycol—identify by specific laboratory tests and clinical history 1, 2
- Alcoholic ketoacidosis: Distinguished by clinical history and glucose levels 1, 2
- Chronic renal failure: Consider bicarbonate levels 1, 2
- Starvation ketosis: Differentiate by bicarbonate levels 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