Diagnostic Criteria for Diabetic Ketoacidosis (DKA)
DKA is diagnosed when all three core criteria are present: blood glucose >250 mg/dL, venous pH <7.3, serum bicarbonate <15 mEq/L, and moderate ketonuria or ketonemia. 1
Core Diagnostic Triad
The American Diabetes Association establishes that DKA requires simultaneous presence of:
- Hyperglycemia: Blood glucose >250 mg/dL 1, 2
- Metabolic acidosis: Venous pH <7.3 AND serum bicarbonate <15 mEq/L 1, 2
- Ketosis: Moderate ketonuria or ketonemia (preferably measured as β-hydroxybutyrate in blood) 1
- Anion gap: Elevated anion gap >10-12 mEq/L, calculated as [Na⁺] - ([Cl⁻] + [HCO₃⁻]) 1, 2
Severity Classification
Once DKA is diagnosed, severity stratification guides management intensity:
Mild DKA 1
- Venous pH: 7.25-7.30
- Bicarbonate: 15-18 mEq/L
- Mental status: Alert
Moderate DKA 1
- Venous pH: 7.00-7.24
- Bicarbonate: 10-15 mEq/L
- Mental status: Drowsy/lethargic
Severe DKA 1
- Venous pH: <7.00
- Bicarbonate: <10 mEq/L
- Mental status: Stuporous or comatose
- Requires intensive monitoring including potential central venous and intra-arterial pressure monitoring 1
Essential Laboratory Workup
Upon presentation with suspected DKA, obtain immediately:
- Complete metabolic panel (electrolytes, BUN, creatinine, glucose) 1
- Venous blood gas (arterial not necessary after initial diagnosis) 1
- Serum β-hydroxybutyrate (preferred over urine ketones) 1
- Complete blood count with differential 1, 3
- Urinalysis 1
- Calculated anion gap and corrected sodium 1
Additional tests to consider based on clinical presentation:
- Bacterial cultures (blood, urine, throat) if infection suspected 1
- Electrocardiography to assess for cardiac complications and potassium abnormalities 3
- Amylase, lipase, hepatic transaminases, troponin, creatine kinase if clinically indicated 3
- Chest radiography if respiratory symptoms present 3
Critical Diagnostic Nuances
Euglycemic DKA
A major pitfall is missing DKA when glucose is <250 mg/dL. Euglycemic DKA is increasingly recognized and can occur with:
- SGLT2 inhibitor use 4, 3, 5
- Ketogenic/low-carbohydrate diets 4, 5
- Recent insulin administration 4
- Pregnancy 4
- Decreased caloric intake or heavy alcohol consumption 4
- Chronic liver disease 4
In euglycemic DKA, the diagnosis still requires pH <7.3, bicarbonate <18 mEq/L, and elevated ketones, but glucose may be <200-250 mg/dL 4, 5. Do not exclude DKA based solely on normal glucose levels if acidosis and ketosis are present. 4
Ketone Measurement
- Direct blood β-hydroxybutyrate measurement is strongly preferred over nitroprusside-based urine or serum tests 1, 6
- Nitroprusside methods only detect acetoacetate and acetone, completely missing β-hydroxybutyrate—the predominant ketoacid in DKA 1, 6
- During treatment, β-hydroxybutyrate converts to acetoacetate, paradoxically making nitroprusside tests appear worse even as the patient improves 1
Venous vs. Arterial Blood Gas
- Venous pH is sufficient for both diagnosis and monitoring after initial assessment 1, 6
- Venous pH typically runs 0.03 units lower than arterial pH 1, 6
- Repeated arterial blood gases are unnecessary and cause patient discomfort 1
Corrected Sodium Calculation
Always correct serum sodium for hyperglycemia using the formula: 1
Corrected Na⁺ = Measured Na⁺ (mEq/L) + [(Glucose (mg/dL) - 100) / 100] × 1.6
This prevents misinterpretation of sodium status during treatment.
Common Diagnostic Pitfalls to Avoid
- Relying on urine ketones alone for diagnosis or monitoring—they are unreliable and misleading 1, 6
- Excluding DKA based on normal or near-normal glucose in the era of SGLT2 inhibitors and ketogenic diets 4, 3, 5
- Obtaining repeated arterial blood gases when venous pH adequately monitors acidosis resolution 1, 6
- Failing to calculate anion gap and corrected sodium, which provide critical diagnostic and management information 1
- Missing type 2 diabetes as a cause—DKA occurs in both type 1 and type 2 diabetes, including severe forms 7