Laboratory Findings for Diabetic Ketoacidosis (DKA)
DKA is diagnosed by the triad of metabolic acidosis (pH <7.3, serum bicarbonate <18 mEq/L, anion gap >10 mEq/L), elevated ketones (preferably β-hydroxybutyrate in blood), and typically hyperglycemia >250 mg/dL—though hyperglycemia has been de-emphasized in recent guidelines due to increasing recognition of euglycemic DKA. 1, 2
Core Diagnostic Laboratory Criteria
The essential laboratory findings that define DKA include:
Metabolic Acidosis
- pH <7.3 (arterial blood gas)
- Serum bicarbonate <18 mEq/L
- Anion gap >10 mEq/L (some sources use ≥15 mEq/L) 1, 3
Ketone Bodies
- β-hydroxybutyrate (β-OHB) measurement in blood is preferred over urine ketones for both diagnosis and monitoring 2
- β-OHB ≥1.5 mmol/L has 98% sensitivity and 85% specificity for DKA 4
- Traditional nitroprusside-based urine tests detect only acetoacetate and acetone, not β-OHB, which is the predominant ketone body in DKA and can lead to underestimation of ketosis 2
Glucose
- Traditionally >250 mg/dL, but euglycemic DKA (glucose <250 mg/dL or even normal) is increasingly recognized, particularly with SGLT2 inhibitor use 1, 5
- Hyperglycemia should not be overemphasized as an absolute requirement
Additional Laboratory Abnormalities
Electrolyte Disturbances
- Hyperkalemia is common on presentation despite total body potassium depletion (due to acidosis shifting potassium extracellularly) 6
- Sodium, chloride, and other electrolyte abnormalities from osmotic diuresis 6
- Elevated anion gap from accumulation of ketoacids
Other Findings
- Elevated blood urea nitrogen (BUN) and creatinine from dehydration and prerenal azotemia
- Leukocytosis (even without infection)
- Elevated phosphate levels may occur 7
- Hemoglobin A1C helps assess chronic glycemic control 3
Critical Pitfalls to Avoid
Do not rely on urine ketone testing alone or nitroprusside-based methods for monitoring DKA treatment, as these do not measure β-OHB and can be misleading 2. The equilibrium shifts toward β-OHB production in DKA, and as treatment progresses, β-OHB converts back to acetoacetate, potentially making urine ketones appear to worsen even as the patient improves.
Do not exclude DKA based solely on normal or mildly elevated glucose, especially in patients taking SGLT2 inhibitors, pregnant patients with diabetes, or those with prolonged vomiting 5. These patients can present with euglycemic DKA where the classic triad is modified to emphasize ketoacidosis over hyperglycemia.
Recommended Laboratory Workup
When DKA is suspected, obtain:
- Arterial or venous blood gas (pH, bicarbonate)
- Blood β-hydroxybutyrate (point-of-care testing available and highly useful at triage) 4
- Complete metabolic panel (glucose, electrolytes, BUN, creatinine, calculate anion gap)
- Phosphate level
- Complete blood count with differential
- Urinalysis
- Hemoglobin A1C
- Electrocardiogram (to assess for hyperkalemia effects and precipitating cardiac events) 1, 3
Consider additional testing based on clinical presentation: blood and urine cultures, chest radiography, amylase/lipase, liver enzymes, troponin, and creatine kinase to identify precipitating causes and complications 1.