What are the diagnostic criteria and treatment for diabetic ketoacidosis (DKA) in a patient with type 2 diabetes mellitus (T2DM)?

Diagnosing DKA in Type 2 Diabetes

Diagnose DKA in type 2 diabetics using the same criteria as type 1 diabetes: blood glucose >250 mg/dL, venous pH <7.3, serum bicarbonate <15 mEq/L, and elevated blood β-hydroxybutyrate (β-OHB), though be alert for euglycemic DKA especially in patients on SGLT2 inhibitors. 1

Core Diagnostic Criteria

The diagnosis requires three components present simultaneously 1:

• Hyperglycemia: Blood glucose >250 mg/dL (though this can be absent in euglycemic DKA) 1
• Metabolic acidosis: Venous pH <7.3 AND serum bicarbonate <15 mEq/L 1
• Ketosis: Elevated blood ketones, preferably measured as β-OHB 2

The anion gap should be calculated as [Na⁺] - ([Cl⁻] + [HCO₃⁻]) and will typically be >10-12 mEq/L in DKA. 1

Essential Laboratory Workup

Obtain immediately upon presentation 1, 3:

• Complete metabolic panel (electrolytes, BUN, creatinine, glucose)
• Venous blood gas (arterial not necessary for initial diagnosis)
• Blood β-hydroxybutyrate (β-OHB) - this is the preferred ketone measurement 2
• Complete blood count
• Urinalysis
• Serum osmolality
• Electrocardiogram 3

If infection suspected, add blood cultures, urine cultures, throat cultures, and chest X-ray as clinically indicated 3.

Critical Ketone Measurement Considerations

Use direct blood β-OHB measurement, NOT urine ketones or nitroprusside-based tests. 2 Here's why this matters:

• The nitroprusside method (urine dipsticks, serum ketone tests) only measures acetoacetate and acetone, completely missing β-OHB, which is the predominant ketone in DKA 2
• β-OHB levels ≥3.0 mmol/L in children or ≥3.8 mmol/L in adults strongly suggest DKA 4
• Research suggests optimal cut-off values of 6.3 mmol/L for β-OHB may be more specific for DKA diagnosis 5
• Point-of-care β-OHB testing has 98% sensitivity and 85% specificity for DKA at levels ≥1.5 mmol/L 6

Severity Classification

Once diagnosed, classify severity to guide management intensity 1:

• Mild DKA: pH 7.25-7.30, bicarbonate 15-18 mEq/L, alert mental status
• Moderate DKA: pH 7.00-7.24, bicarbonate 10-15 mEq/L, drowsy/lethargic
• Severe DKA: pH <7.00, bicarbonate <10 mEq/L, stuporous or comatose (requires ICU-level monitoring) 1

Special Considerations for Type 2 Diabetes

Although DKA is less common in type 2 diabetes, it absolutely can occur and requires the same diagnostic approach. 2 Key points:

• SGLT2 inhibitors significantly increase DKA risk in type 2 diabetics and commonly cause euglycemic DKA (glucose <250 mg/dL with ketoacidosis) 2, 7
• In euglycemic DKA, the diagnosis relies heavily on pH, bicarbonate, anion gap, and β-OHB rather than glucose 7
• Patients on SGLT2 inhibitors should check blood ketones (not urine) during any illness or unexplained symptoms 2

Common Diagnostic Pitfalls to Avoid

• Do not rely on urine ketones for diagnosis - they miss β-OHB and can be falsely negative early in DKA 2
• Do not dismiss DKA possibility because glucose is <250 mg/dL - euglycemic DKA is increasingly common, especially with SGLT2 inhibitors 2, 7
• Do not use arterial blood gas when venous is sufficient - venous pH is typically only 0.03 units lower than arterial and is adequate for diagnosis 1
• Do not forget to correct sodium for hyperglycemia: Add 1.6 mEq/L to measured sodium for every 100 mg/dL glucose above 100 mg/dL 1

Monitoring During Treatment

Once DKA is diagnosed, draw blood every 2-4 hours to measure 1, 8:

• Electrolytes (especially potassium)
• Glucose
• Venous pH
• β-OHB (if available)
• Anion gap
• BUN/creatinine
• Serum osmolality

Resolution is confirmed when ALL of the following are met: glucose <200 mg/dL, venous pH >7.3, serum bicarbonate ≥18 mEq/L, and anion gap ≤12 mEq/L. 1, 8