What are the key lab findings in diabetic ketoacidosis (DKA)?

Laboratory Findings in Diabetic Ketoacidosis (DKA)

The American Diabetes Association establishes that DKA is diagnosed by the simultaneous presence of three core laboratory abnormalities: 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 Laboratory Criteria

Glucose

• Plasma glucose >250 mg/dL is the traditional threshold for DKA diagnosis 1
• However, euglycemic DKA (glucose <200-250 mg/dL) is increasingly recognized, particularly with SGLT2 inhibitor use, pregnancy, heavy alcohol use, or when patients maintain insulin administration with reduced carbohydrate intake 1, 2
• Despite euglycemia, the metabolic acidosis and ketosis criteria must still be met for DKA diagnosis 1

Acid-Base Status

• Arterial pH <7.3 is required for diagnosis 1
• Serum bicarbonate <18 mEq/L is required for diagnosis 3, 1
• Elevated anion gap >10 mEq/L (mild DKA) or >12 mEq/L (moderate to severe DKA) is characteristic 3
• A critical pitfall: approximately 23% of DKA cases can present with pH >7.4 (diabetic ketoalkalosis) due to concurrent metabolic alkalosis or respiratory alkalosis, yet still have severe ketoacidosis requiring full DKA treatment 4

Ketone Bodies

• Blood β-hydroxybutyrate (β-OHB) measurement is the preferred diagnostic method rather than nitroprusside-based tests 1
• This is crucial because nitroprusside methods (urine dipsticks, serum tablets) only detect acetoacetate and acetone, NOT β-OHB, which is the predominant ketone in DKA 1
• During treatment, β-OHB converts to acetoacetate, making nitroprusside tests falsely suggest worsening ketosis when the patient is actually improving 1

Severity Stratification Based on Laboratory Values

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

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

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

Complete Initial Laboratory Workup

When DKA is suspected, obtain the following immediately 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 β-hydroxybutyrate (preferred) or serum/urine ketones 1
• Serum osmolality 1
• Complete blood count with differential 1
• Urinalysis 1
• Electrocardiogram 1

Additional tests to consider based on clinical presentation include amylase, lipase, hepatic transaminases, troponin, creatine kinase, blood and urine cultures, and chest radiography 5

Laboratory Criteria for DKA Resolution

DKA is considered resolved when ALL of the following are achieved 1:

• Glucose <200 mg/dL 1
• Serum bicarbonate ≥18 mEq/L 3, 1
• Venous pH >7.3 3, 1

During treatment, monitor venous pH and anion gap every 2-4 hours to track resolution of acidosis 3

Critical Differential Diagnosis Considerations

Alcoholic Ketoacidosis

• Glucose is typically normal, low, or only mildly elevated (rarely >250 mg/dL), which distinguishes it from DKA 6
• Presents with elevated anion gap metabolic acidosis and ketosis 6
• Serum bicarbonate is typically not as low as 18 mEq/L 6

Starvation Ketosis

• Serum bicarbonate is usually not lower than 18 mEq/L, helping distinguish it from DKA 3
• Less severe acidosis and lower ketone levels than DKA 1