Diagnostic Criteria for Diabetic Ketoacidosis (DKA)
DKA is diagnosed when blood glucose is >250 mg/dL (or history of diabetes), venous pH is <7.3, serum bicarbonate is <15 mEq/L, and moderate ketonuria or ketonemia is present. 1
Core Diagnostic Triad
The American Diabetes Association defines DKA using three essential components 1:
- Hyperglycemia: Blood glucose >250 mg/dL 1
- Metabolic acidosis: Venous pH <7.3 AND serum bicarbonate <15 mEq/L 1
- Ketosis: Moderate ketonuria or ketonemia (preferably measured as β-hydroxybutyrate) 1
The anion gap should be calculated using [Na⁺] - ([Cl⁻] + [HCO₃⁻]) and is typically >10-12 mEq/L in DKA 1.
Severity Classification
DKA severity is stratified based on pH and bicarbonate levels 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 mental status 1
- Severe DKA: Venous pH <7.00, bicarbonate <10 mEq/L, associated with higher morbidity and mortality 1
Important Exception: Euglycemic DKA
Approximately 10% of DKA cases present with euglycemic DKA, defined as plasma glucose <200 mg/dL despite meeting other criteria for ketoacidosis. 2
Euglycemic DKA occurs in specific clinical contexts 2:
- SGLT2 inhibitor use (risk 0.6-4.9 events per 1,000 patient-years) 2
- Pregnancy (up to 2% of pregnancies with pregestational diabetes) 2
- Reduced food intake/starvation 2
- Chronic alcohol use or liver disease 2
- Glycogen storage disorders 2
In these cases, DKA diagnosis requires insulin deficiency with venous pH <7.3 and serum bicarbonate <15 mEq/L, regardless of glucose level 2.
Essential Laboratory Evaluation
Upon presentation, immediately obtain 1:
- Complete metabolic panel (electrolytes, BUN, creatinine) 1
- Venous blood gas (arterial not required after initial diagnosis) 1
- Serum ketones (β-hydroxybutyrate preferred) 1
- Complete blood count 1
- Urinalysis 1
- Anion gap calculation 1
Correct serum sodium for hyperglycemia using: [measured Na (mEq/L)] + [glucose (mg/dL) - 100]/100 × 1.6 1.
Resolution Criteria
DKA is considered resolved when ALL of the following are met 3:
Critical Pitfalls to Avoid
Do not rely on urine ketones or the nitroprusside method for diagnosis or monitoring, as these only measure acetoacetate and acetone, not β-hydroxybutyrate, which is the predominant ketone body in DKA 1. Direct blood β-hydroxybutyrate measurement is the gold standard 1.
Do not assume normal glucose excludes DKA—always consider euglycemic DKA in patients on SGLT2 inhibitors, pregnant patients, or those with reduced oral intake 2.
After initial arterial blood gas, venous pH (typically 0.03 units lower than arterial) is sufficient for monitoring and avoids unnecessary arterial punctures 1.