Baseline Laboratory Evaluation for Diabetic Ketoacidosis
For DKA diagnosis and management, immediately obtain arterial blood gases, serum glucose, electrolytes with calculated anion gap, serum β-hydroxybutyrate (not nitroprusside-based tests), bicarbonate, BUN/creatinine, and urinalysis. 1
Essential Diagnostic Labs (Obtain Immediately)
Core Metabolic Parameters
- Arterial blood gases to document metabolic acidosis with pH <7.3 1, 2
- Serum glucose (typically >250 mg/dL in classic DKA, though euglycemic variants exist with glucose <250 mg/dL) 1, 3
- Serum bicarbonate to confirm levels <15-18 mEq/L 1, 2
- Serum β-hydroxybutyrate specifically—this is the predominant ketone and must be measured directly 1, 2
Electrolytes and Renal Function
- Complete metabolic panel including sodium, potassium, chloride, and calculated anion gap (should be >10-12 mEq/L in DKA) 1, 2
- BUN and creatinine to assess renal function and hydration status 1, 3
- Corrected sodium: Add 1.6 mEq/L to measured sodium for each 100 mg/dL glucose above 100 mg/dL 1, 2
Additional Initial Tests
- Complete blood count with differential to evaluate for underlying infection 2, 3
- Urinalysis with urine ketones by dipstick (supportive evidence only, not diagnostic alone) 3, 4
- Serum osmolality (calculated) to help differentiate from other causes of acidosis 3
Additional Labs to Consider Based on Clinical Context
- Bacterial cultures (blood, urine, throat) if infection is suspected as a precipitating factor 2
- Electrocardiography to identify cardiac complications and monitor for electrolyte abnormalities 4
- A1C to assess chronic glycemic control 4
- Amylase, lipase, hepatic transaminases if abdominal pain is prominent 4
- Troponin and creatine kinase if cardiac ischemia is suspected 4
- Chest radiography if respiratory symptoms or infection is suspected 4
Critical Diagnostic Pitfalls to Avoid
Never rely on nitroprusside-based ketone tests (urine or serum) for diagnosis or monitoring. These tests only measure acetoacetate and acetone, completely missing β-hydroxybutyrate, which is the predominant and strongest ketoacid in DKA. 1, 2 During treatment, β-hydroxybutyrate converts to acetoacetate, paradoxically making nitroprusside tests appear worse even as the patient improves. 2
Do not use urine ketone testing alone for diagnosis—it is insufficient and may be misleading. 1, 3
After initial diagnosis, venous pH suffices for monitoring—repeated arterial blood gases are generally unnecessary, as venous pH typically runs 0.03 units lower than arterial pH and adequately monitors acidosis resolution. 2
Monitoring Labs During Treatment
Once DKA management begins, repeat the following every 2-4 hours: 1, 2
- Electrolytes (sodium, potassium, chloride, bicarbonate)
- Serum glucose
- BUN and creatinine
- Serum osmolality
- Venous pH (arterial not needed after initial diagnosis)
- β-hydroxybutyrate
Track vital signs, fluid input/output, mental status continuously, and monitor for hemodynamic improvement in blood pressure. 1
Severity Classification Based on Labs
- Mild DKA: pH 7.25-7.30, bicarbonate 15-18 mEq/L 2
- Moderate DKA: pH 7.00-7.24, bicarbonate 10-15 mEq/L 2
- Severe DKA: pH <7.00, bicarbonate <10 mEq/L (requires intensive monitoring, potentially central venous and intra-arterial pressure monitoring) 2
Resolution Criteria (When to Stop Intensive Monitoring)
DKA is resolved when all of the following are met: 2
- Glucose <200 mg/dL
- Venous pH >7.3
- Serum bicarbonate ≥18 mEq/L
- Anion gap ≤12 mEq/L
Note that ketonemia typically takes longer to clear than hyperglycemia, requiring continued monitoring even after glucose normalizes. 2
Differential Diagnosis Labs
Exclude other causes of high anion gap metabolic acidosis: 1, 3
- Lactic acidosis (lactate level)
- Salicylate toxicity (salicylate level)
- Methanol or ethylene glycol ingestion (osmolar gap, toxicology screen)
- Uremia (BUN/creatinine)
- Alcoholic ketoacidosis (history, ketone pattern)