Diagnostic Criteria for Diabetic Ketoacidosis
Diabetic ketoacidosis is diagnosed when all three of the following criteria are simultaneously present: hyperglycemia (plasma glucose >250 mg/dL), metabolic acidosis (arterial pH <7.3 AND serum bicarbonate <18 mEq/L), and positive ketones in blood or urine. 1
Core Diagnostic Triad
All three criteria must be met simultaneously to establish the diagnosis: 1
- Hyperglycemia: Plasma glucose >250 mg/dL 2, 3
- Metabolic acidosis: Arterial pH <7.3 AND serum bicarbonate <18 mEq/L 2, 3
- Ketosis: Positive serum or urine ketones 2, 3
Severity Stratification
DKA severity is classified based on the degree of acidosis and mental status: 2
- Mild DKA: pH 7.25-7.30, bicarbonate 15-18 mEq/L, anion gap >10 mEq/L, alert mental status 2
- Moderate DKA: pH 7.00-7.24, bicarbonate 10 to <15 mEq/L, anion gap >12 mEq/L, alert/drowsy 2
- Severe DKA: pH <7.00, bicarbonate <10 mEq/L, anion gap >12 mEq/L, stupor/coma 2, 3
Essential Laboratory Workup
When DKA is suspected, immediately obtain: 2, 3
- Plasma glucose 2, 3
- Arterial blood gas (pH, bicarbonate) or venous pH 2, 3
- Serum electrolytes with calculated anion gap 2, 3
- Blood urea nitrogen/creatinine 2, 3
- Serum β-hydroxybutyrate (preferred) or serum/urine ketones 2, 3
- Serum osmolality 2
- Complete blood count with differential 2, 3
- Urinalysis 2, 3
- Electrocardiogram 2
Critical Ketone Measurement Pitfall
β-hydroxybutyrate measurement in blood is the preferred method for diagnosing DKA, not nitroprusside-based tests. 2, 3 This is crucial because:
- Nitroprusside methods (urine dipsticks, serum tablets) only detect acetoacetate and acetone, NOT β-hydroxybutyrate 2, 4
- β-hydroxybutyrate is the predominant ketone body in DKA 2, 3
- During treatment, β-hydroxybutyrate converts to acetoacetate, making nitroprusside tests falsely suggest worsening ketosis when the patient is actually improving 2
Euglycemic DKA: A Diagnostic Challenge
Approximately 10% of DKA cases present with euglycemic DKA (plasma glucose <200 mg/dL). 1 DKA diagnosis requires either the presence of hyperglycemia OR prior history of diabetes. 1
Euglycemic DKA is associated with: 1, 2
- SGLT2 inhibitor therapy (most common modern cause) 2
- Reduced food intake or starvation 1
- Pregnancy 1
- Alcohol use 1
- Chronic liver disease 1
In euglycemic DKA, the diagnosis still requires metabolic acidosis (pH <7.3, bicarbonate <18 mEq/L) and elevated β-hydroxybutyrate, despite glucose <250 mg/dL. 2
Differential Diagnosis
DKA must be distinguished from other causes of high anion gap metabolic acidosis: 2, 3
- Alcoholic ketoacidosis: Clinical history of alcohol use, glucose typically normal to mildly elevated (rarely >250 mg/dL) or hypoglycemic, less severe acidosis (bicarbonate typically not <18 mEq/L) 2, 4
- Starvation ketosis: Serum bicarbonate not lower than 18 mEq/L, less severe acidosis, prolonged fasting history 2
- Lactic acidosis 2, 3
- Toxic ingestions (salicylate, methanol, ethylene glycol) 3
Resolution Criteria
DKA is considered resolved when: 2