What capillary blood glucose (CBG) level is indicative of diabetic ketoacidosis (DKA)?

Blood Glucose Threshold for DKA Diagnosis

The diagnostic threshold for DKA is a blood glucose >250 mg/dL, combined with venous pH <7.3, bicarbonate <15 mEq/L, and moderate ketonuria or ketonemia. 1

Standard Diagnostic Criteria

The American Diabetes Association establishes the following glucose-based criteria for DKA diagnosis:

• Blood glucose >250 mg/dL is the standard threshold for DKA diagnosis in both adults and pediatric patients 1
• This glucose level must be accompanied by:
  • Venous pH <7.3 1
  • Serum bicarbonate <15 mEq/L 1
  • Moderate ketonuria or ketonemia 1
  • Anion gap >10 mEq/L (mild DKA) or >12 mEq/L (moderate to severe DKA) 2

Critical Caveat: Euglycemic DKA

A major diagnostic pitfall is euglycemic DKA, where patients present with blood glucose <250 mg/dL (or even <200 mg/dL) but still have ketoacidosis. 3, 4

Common causes of euglycemic DKA include:

• Recent insulin use prior to arrival (57% of cases) 4
• Poor oral intake with baseline insulin use (29% of cases) 4
• SGLT2 inhibitor use (14% of cases) - this is an increasingly recognized cause 3, 4
• Pregnancy, heavy alcohol consumption, chronic liver disease 3

Clinical implication: Do not rule out DKA based solely on a "normal" glucose level. If a diabetic patient presents with metabolic acidosis (pH <7.3, bicarbonate <18 mEq/L) and elevated ketones, treat as DKA regardless of glucose level. 3, 4

Practical Diagnostic Approach

When evaluating for DKA at triage or in the emergency department:

1. Measure capillary blood glucose - if >250 mg/dL, strongly consider DKA 1
2. Check beta-hydroxybutyrate (β-OHB) using point-of-care testing:
   • β-OHB >3.0 mmol/L has 99.87% sensitivity and 92.89% specificity for DKA 5
   • This is superior to urine ketones (sensitivity 89.89%, specificity only 52.73%) 5
   • β-OHB >1.5 mmol/L at triage has 98% sensitivity for DKA 6
3. Obtain venous blood gas and basic metabolic panel to confirm pH <7.3, bicarbonate <15 mEq/L, and anion gap >10-12 mEq/L 1, 2

The glucose threshold of >250 mg/dL should be viewed as a guideline, not an absolute rule - always consider the complete clinical picture including pH, bicarbonate, ketones, and anion gap. 7, 3