What tests should be ordered in a patient suspected of having diabetic ketoacidosis (DKA)?

Tests to Order in Suspected DKA

Order a complete metabolic panel, venous blood gas, blood β-hydroxybutyrate, complete blood count with differential, urinalysis, and electrocardiogram immediately upon presentation of suspected diabetic ketoacidosis. 1, 2, 3

Essential Diagnostic Tests

Core Laboratory Panel

• Blood glucose is required to confirm hyperglycemia (typically >250 mg/dL), though euglycemic DKA can occur, especially with SGLT2 inhibitors 1, 3
• Venous blood gas measures pH and bicarbonate—DKA requires pH <7.3 and bicarbonate <15 mEq/L 1, 3
• Complete metabolic panel including sodium, potassium, chloride, bicarbonate, BUN, and creatinine is essential 1, 2, 3
• Blood β-hydroxybutyrate (β-OHB) is the preferred method for diagnosing and monitoring DKA—do not rely on urine ketones or nitroprusside-based tests 4, 1, 3
• Anion gap must be calculated using [Na⁺] - ([Cl⁻] + [HCO₃⁻]), which should be >10-12 mEq/L in DKA 1, 2, 3
• Serum osmolality assesses hyperosmolar state 2, 3

Additional Essential Tests

• Complete blood count with differential identifies infection or other precipitating factors 1, 2, 3
• Urinalysis screens for infection and documents glycosuria/ketonuria 1, 2, 3
• Electrocardiogram detects cardiac complications and monitors for potassium-related arrhythmias 1, 2, 3
• HbA1c distinguishes acute decompensation from chronic poor control 2, 3

Tests When Infection is Suspected

• Bacterial cultures of urine, blood, and throat should be obtained if infection is suspected as a precipitating factor 1
• Consider chest radiography if pneumonia is suspected 5
• Additional tests like amylase, lipase, hepatic transaminases, troponin, and creatine kinase may be warranted based on clinical presentation 5

Critical Diagnostic Pitfall to Avoid

Never use nitroprusside-based ketone tests (urine or serum) for diagnosis or monitoring of DKA. These tests only measure acetoacetate and acetone, completely missing β-hydroxybutyrate—the predominant ketoacid in DKA. During treatment, β-hydroxybutyrate converts to acetoacetate, making nitroprusside tests paradoxically appear worse even as the patient improves. 4, 1, 3

Severity Classification After Initial Testing

Once DKA is confirmed, classify severity to guide monitoring intensity: 1, 2, 3

• 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/comatose—requires intensive monitoring including possible central venous and intra-arterial pressure monitoring

Monitoring During Treatment

• Repeat labs every 2-4 hours for electrolytes, glucose, BUN, creatinine, osmolality, venous pH, β-hydroxybutyrate, and anion gap 1, 3
• Avoid repeated arterial blood gases—venous pH (typically 0.03 units lower than arterial) is sufficient for monitoring after initial diagnosis 1, 3
• Corrected sodium should be calculated by adding 1.6 mEq/L for every 100 mg/dL glucose above 100 mg/dL 1, 3

Resolution Criteria

DKA is resolved when all of the following are met: 1, 2, 3

• Glucose <200 mg/dL
• Venous pH >7.3
• Serum bicarbonate ≥18 mEq/L
• Anion gap ≤12 mEq/L

Note that ketonemia clears more slowly than hyperglycemia, so continue monitoring β-hydroxybutyrate until normalized even after other parameters resolve. 1, 3

Special Consideration for Potassium

Measure potassium immediately before starting insulin. If initial potassium is <3.3 mEq/L, delay insulin therapy and aggressively replace potassium first to prevent fatal cardiac arrhythmias. 1, 2, 3