What are the diagnostic criteria for Diabetic Ketoacidosis (DKA)?

Diagnostic Criteria for Diabetic Ketoacidosis (DKA)

DKA is diagnosed when all three of the following criteria are 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

The diagnosis requires simultaneous presence of:

• Hyperglycemia: Plasma glucose >250 mg/dL 1
• Metabolic acidosis: Arterial pH <7.3 AND serum bicarbonate <18 mEq/L 1, 2
• Ketosis: Positive serum or urine ketones 1

Severity Classification

DKA severity is stratified based on the degree of acidosis and mental status 1:

Mild DKA

• Plasma glucose >250 mg/dL 1
• Arterial pH 7.25–7.30 1
• Serum bicarbonate 15–18 mEq/L 1
• Anion gap >10 mEq/L 1
• Mental status: Alert 1

Moderate DKA

• Plasma glucose >250 mg/dL 1
• Arterial pH 7.00–7.24 1
• Serum bicarbonate 10 to <15 mEq/L 1
• Anion gap >12 mEq/L 1
• Mental status: Alert/drowsy 1

Severe DKA

• Plasma glucose >250 mg/dL 1
• Arterial pH <7.00 1
• Serum bicarbonate <10 mEq/L 1
• Anion gap >12 mEq/L 1
• Mental status: Stupor/coma 1

Critical Laboratory Measurements

Ketone Testing

β-hydroxybutyrate (βOHB) measurement in blood is the preferred method for diagnosing DKA and should be used instead of nitroprusside-based tests. 1

• Nitroprusside methods (urine dipsticks, serum tablets) only detect acetoacetate and acetone, NOT βOHB, which is the predominant ketone in DKA 1
• During treatment, βOHB converts to acetoacetate, making nitroprusside tests falsely suggest worsening ketosis 1
• Blood βOHB >1.5-3.0 mmol/L supports DKA diagnosis 3

Anion Gap

• Calculate as: (Na+) - (Cl- + HCO3-) 1
• Anion gap >10 mEq/L in mild DKA, >12 mEq/L in moderate-severe DKA 1

Effective Serum Osmolality

• Calculate as: 2[measured Na (mEq/L)] + glucose (mg/dL)/18 1
• Variable in DKA (distinguishes from HHS where it's >320 mOsm/kg) 1

Important Clinical Caveats

Euglycemic DKA

Hyperglycemia has been de-emphasized in recent guidelines due to increasing recognition of euglycemic DKA, where glucose may be <250 mg/dL or even <200 mg/dL. 2, 4

• SGLT2 inhibitors significantly increase risk of euglycemic DKA by promoting urinary glucose excretion 1, 3
• Other causes include: starvation, pregnancy, chronic liver disease, recent insulin use, heavy alcohol consumption 5, 4
• Diagnosis still requires metabolic acidosis (pH <7.3, bicarbonate <18 mEq/L) and elevated ketones, regardless of glucose level 2, 4

Differential Diagnosis

DKA must be distinguished from other causes of high anion gap metabolic acidosis 1:

• Alcoholic ketoacidosis (AKA): Glucose typically normal to mildly elevated (rarely >250 mg/dL) or hypoglycemic, distinguished by clinical history of alcohol use 1, 6
• Starvation ketosis: Serum bicarbonate usually not lower than 18 mEq/L 1, 6
• Lactic acidosis: Measure blood lactate 1
• Toxic ingestions: Salicylates, methanol, ethylene glycol—check drug levels and look for osmolar gap 1

Essential Initial Laboratory Workup

When DKA is suspected, obtain 1:

• Plasma glucose 1
• Arterial blood gas (pH, bicarbonate) or venous pH 1
• Serum electrolytes with calculated anion gap 1
• Blood urea nitrogen/creatinine 1
• Serum βOHB (preferred) or serum/urine ketones 1
• Serum osmolality 1
• Complete blood count with differential 1
• Urinalysis 1
• Electrocardiogram 1

Resolution Criteria

DKA is considered resolved when glucose <200 mg/dL, serum bicarbonate ≥18 mEq/L, and venous pH >7.3. 1