Classification of Diabetic Ketoacidosis (DKA)
DKA is diagnosed when all three core criteria are simultaneously present: blood glucose >250 mg/dL (though this threshold is increasingly de-emphasized due to euglycemic DKA), venous pH <7.3, and serum bicarbonate <15 mEq/L, with elevated blood β-hydroxybutyrate. 1, 2
Core Diagnostic Criteria
All three components must be present simultaneously for DKA diagnosis:
- Hyperglycemia: Blood glucose >250 mg/dL, though this threshold has been de-emphasized in recent guidelines due to increasing incidence of euglycemic DKA, particularly in patients on SGLT2 inhibitors 1, 3
- Metabolic acidosis: Venous pH <7.3 AND serum bicarbonate <15 mEq/L 1, 2
- Ketosis: Elevated blood β-hydroxybutyrate (β-OHB), which is the preferred ketone measurement—NOT urine ketones or nitroprusside-based tests 1, 4
- Anion gap: Should be >10-12 mEq/L, calculated as [Na⁺] - ([Cl⁻] + [HCO₃⁻]) 1, 2
Severity Classification
DKA severity is classified into three categories based on pH, bicarbonate, anion gap, and mental status, which directly correlates with ICU admission rates, mortality, and healthcare costs. 1, 5
Mild DKA
- Venous pH: 7.25-7.30 1, 2
- Serum bicarbonate: 15-18 mEq/L 1, 2
- Anion gap: >10 mEq/L 1
- Mental status: Alert 1, 2
Moderate DKA
- Venous pH: 7.00-7.24 1, 2
- Serum bicarbonate: 10-15 mEq/L 1, 2
- Anion gap: >12 mEq/L 1
- Mental status: Drowsy/lethargic 1, 2
- ICU care required in 6.7% of cases 5
- Mortality rate: 13.3% 5
Severe DKA
- Venous pH: <7.00 1, 2
- Serum bicarbonate: <10 mEq/L 1, 2
- Anion gap: >12 mEq/L 1
- Mental status: Stuporous or comatose 1, 2
- ICU care required in 47.4% of cases 5
- Invasive ventilation required in 47% of cases 5
- Mortality rate: 26% 5
- Mean healthcare expenditure significantly higher (₹64,000 vs ₹29,000-30,000 for mild/moderate) 5
Essential Laboratory Workup for Classification
- Complete metabolic panel (sodium, potassium, chloride, bicarbonate, BUN, creatinine, glucose) 1
- Venous blood gas (pH, pCO2, bicarbonate) 1, 2
- Blood β-hydroxybutyrate measurement (gold standard)—NOT urine ketones 1, 4
- Complete blood count with differential 1, 4
- Urinalysis 1, 4
- Serum osmolality 1, 4
- Electrocardiogram 1, 4
- Anion gap calculation 1, 2
Special Classification Considerations
Euglycemic DKA
- Blood glucose may be <250 mg/dL while still meeting criteria for DKA (pH <7.3, bicarbonate <15 mEq/L, elevated ketones) 1, 3
- Increasingly common with SGLT2 inhibitor use 1, 4, 6
- Same severity classification applies based on pH and bicarbonate levels 6
Diabetic Ketoalkalosis
- A commonly overlooked alkalemic variant where pH >7.4 despite presence of ketoacidosis 7
- Accounts for 23.3% of DKA presentations 7
- All cases have increased anion gap metabolic acidosis present 7
- 34% have severe ketoacidosis (β-OHB ≥3 mmol/L) requiring same treatment as traditional DKA 7
- Associated with concurrent metabolic alkalosis (47.2%), respiratory alkalosis (81.1%), or respiratory acidosis (11.3%) 7
Critical Pitfalls to Avoid in Classification
- Never rely on urine ketones or nitroprusside-based tests for diagnosis or classification—these only measure acetoacetate and acetone, completely missing β-hydroxybutyrate, the predominant ketone in DKA 1, 4
- Do not dismiss DKA because glucose is <250 mg/dL—euglycemic DKA is increasingly common, especially with SGLT2 inhibitors 1, 4
- Do not overlook diabetic ketoalkalosis—patients with pH >7.4 can still have severe ketoacidosis requiring full DKA treatment 7
- Nitroprusside tests can paradoxically worsen during treatment as β-hydroxybutyrate converts to acetoacetate, falsely suggesting worsening ketosis 1, 4
Resolution Criteria (When DKA Classification No Longer Applies)
DKA is resolved when ALL of the following are met: