Diagnostic Criteria for Diabetic Ketoacidosis (DKA)
DKA is diagnosed when all three of the following criteria are simultaneously present: 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 Triad
The diagnosis requires three components present at the same time 2:
1. Hyperglycemia
- Blood glucose >250 mg/dL is the traditional threshold 1, 2
- However, euglycemic DKA (glucose <250 mg/dL) is increasingly common, particularly in patients taking SGLT2 inhibitors, so do not dismiss DKA based on glucose alone 2, 3, 4
2. Metabolic Acidosis
- Venous pH <7.3 1, 2
- Serum bicarbonate <15 mEq/L 1, 2
- Anion gap >10-12 mEq/L (calculated as [Na⁺] - ([Cl⁻] + [HCO₃⁻])) 1, 5
3. Ketosis
- Elevated blood β-hydroxybutyrate (β-OHB) is the preferred measurement 1, 2
- Moderate ketonuria or ketonemia 1
Essential Laboratory Workup
Obtain immediately upon presentation 1, 2:
- Complete metabolic panel (electrolytes, BUN, creatinine, glucose) 1, 2
- Venous blood gas (for pH and bicarbonate) 1, 2
- Blood β-hydroxybutyrate (β-OHB)—NOT urine ketones 1, 2
- Complete blood count 1, 2
- Urinalysis 1, 2
- Serum osmolality 2
- Electrocardiogram 2
- Bacterial cultures (urine, blood, throat) if infection suspected 1
Severity Classification
DKA severity determines monitoring intensity and prognosis 1, 5:
Mild DKA
- Venous pH: 7.25-7.30 1, 5
- Serum bicarbonate: 15-18 mEq/L 1, 5
- Mental status: Alert 1, 5
- Anion gap: >10 mEq/L 5
Moderate DKA
- Venous pH: 7.00-7.24 1, 5
- Serum bicarbonate: 10 to <15 mEq/L 1, 5
- Mental status: Drowsy/lethargic 1, 5
- Anion gap: >12 mEq/L 5
Severe DKA
- Venous pH: <7.00 1, 5
- Serum bicarbonate: <10 mEq/L 1, 5
- Mental status: Stupor/coma 1, 5
- Anion gap: >12 mEq/L 5
- Associated with higher morbidity and mortality; requires ICU-level monitoring with central venous and intra-arterial pressure monitoring 1, 5
Critical Pitfalls to Avoid
Do NOT Rely on Urine Ketones or Nitroprusside Tests
The nitroprusside method only measures acetoacetate and acetone, completely missing β-hydroxybutyrate (β-OHB), which is the predominant and strongest ketoacid in DKA. 1, 2 During treatment, β-OHB is converted to acetoacetate, which paradoxically makes nitroprusside tests appear worse even as the patient improves 1. This can lead to falsely negative results early in DKA or falsely suggest worsening ketosis during treatment 1, 2.
Do NOT Dismiss DKA Because Glucose is <250 mg/dL
Euglycemic DKA is increasingly common, especially in patients taking SGLT2 inhibitors, those with starvation, chronic liver disease, pregnancy, or alcohol use 2, 3, 4. Always check for acidosis and ketones when DKA is suspected, regardless of glucose level 2.
Do NOT Use Arterial Blood Gases for Monitoring
After initial diagnosis, venous pH and anion gap adequately monitor acidosis resolution 1. Venous pH is typically 0.03 units lower than arterial pH 1. Repeating arterial sticks is unnecessary and causes patient discomfort 1.
Additional Diagnostic Calculations
- Corrected sodium: Add 1.6 mEq/L for every 100 mg/dL glucose above 100 mg/dL 1
- Anion gap: [Na⁺] - ([Cl⁻] + [HCO₃⁻]) 1, 2