What laboratory abnormalities are seen in diabetic ketoacidosis?

Laboratory Abnormalities in Diabetic Ketoacidosis

Diabetic ketoacidosis is diagnosed by the simultaneous presence of three laboratory abnormalities: hyperglycemia (plasma glucose >250 mg/dL), metabolic acidosis (arterial pH <7.3 AND serum bicarbonate <18 mEq/L), and positive ketones (preferably blood β-hydroxybutyrate). 1

Core Diagnostic Laboratory Triad

All three of the following must be present simultaneously to confirm DKA:

• Hyperglycemia: Plasma glucose >250 mg/dL 1
• Metabolic acidosis: Arterial or venous pH <7.3 AND serum bicarbonate <18 mEq/L 1
• Ketosis: Positive serum or urine ketones, with blood β-hydroxybutyrate being the preferred measurement 1

Complete Initial Laboratory Panel

When DKA is suspected, obtain the following tests promptly:

• Plasma glucose (typically >250 mg/dL) 1
• Arterial or venous blood gas for pH and bicarbonate 1
• Serum electrolytes with calculated anion gap (anion gap >10 mEq/L in mild DKA, >12 mEq/L in moderate-to-severe DKA) 1, 2
• Blood β-hydroxybutyrate (preferred quantitative ketone assay) 1
• Blood urea nitrogen and creatinine 1
• Serum osmolality 1
• Complete blood count with differential 1
• Urinalysis 1
• Electrocardiogram 1

Severity Stratification Based on Laboratory Values

DKA severity is classified by the degree of acidosis and mental status:

• Mild DKA: pH 7.25–7.30, bicarbonate 15–18 mEq/L, anion gap >10 mEq/L, alert mental status 1
• Moderate DKA: pH 7.00–7.24, bicarbonate 10 to <15 mEq/L, anion gap >12 mEq/L, alert to drowsy mental status 1
• Severe DKA: pH <7.00, bicarbonate <10 mEq/L, anion gap >12 mEq/L, stupor or coma 1

Critical Ketone Measurement Pitfall

Blood β-hydroxybutyrate is the only reliable ketone measurement for DKA diagnosis and monitoring. 1 Standard nitroprusside-based urine dipsticks and serum tablets only detect acetoacetate and acetone, NOT β-hydroxybutyrate, which is the predominant ketone body in DKA. 1 During treatment, β-hydroxybutyrate converts to acetoacetate, making nitroprusside tests falsely suggest worsening ketosis when the patient is actually improving. 1

Euglycemic DKA: Important Diagnostic Variant

Approximately 10% of DKA presentations are euglycemic, defined by plasma glucose <200 mg/dL while still meeting acidosis and ketosis criteria. 1 For euglycemic DKA, diagnosis requires:

• Documented hyperglycemia at any point OR known history of diabetes 1
• Metabolic acidosis (pH <7.3, bicarbonate <18 mEq/L) 1
• Elevated blood β-hydroxybutyrate 1

Common precipitating factors for euglycemic DKA include:

• SGLT2-inhibitor therapy (most common modern trigger) 1
• Reduced caloric intake or prolonged fasting 1
• Pregnancy 1
• Alcohol consumption 1
• Chronic liver disease 1

Diabetic Ketoalkalosis: Easily Missed Variant

DKA can present with pH >7.4 (diabetic ketoalkalosis) due to mixed acid-base disorders, occurring in approximately 23% of cases. 3 These patients still have increased anion gap metabolic acidosis (anion gap ≥16 mEq/L) and positive ketones, but concurrent metabolic alkalosis or respiratory alkalosis masks the acidemia. 3 34% of diabetic ketoalkalosis cases have severe ketoacidosis (β-hydroxybutyrate ≥3 mmol/L) and require the same aggressive treatment as traditional DKA. 3

Additional Laboratory Abnormalities to Assess

Beyond the diagnostic triad, evaluate for:

• Corrected serum sodium: Add 1.6 mEq/L for each 100 mg/dL glucose above 100 mg/dL 2
• Serum potassium: Must be >3.3 mEq/L before starting insulin therapy 2
• Phosphate levels 4
• A1C 4
• Amylase, lipase, hepatic transaminases, troponin, creatine kinase (as indicated) 4
• Blood and urine cultures, chest radiography (to identify precipitating causes) 2, 4

Resolution Criteria

DKA is considered resolved when:

• Glucose <200 mg/dL 1, 2
• Serum bicarbonate ≥18 mEq/L 1
• Venous pH >7.3 1, 2
• Normalized anion gap 2