Diagnostic Criteria for Diabetic Ketoacidosis (DKA)
DKA is diagnosed when blood glucose >250 mg/dL (or prior diabetes history), venous pH <7.3, serum bicarbonate <15 mEq/L, and elevated blood β-hydroxybutyrate are all present simultaneously. 1
Core Diagnostic Triad
The diagnosis requires three components present at the same time 2:
- Hyperglycemia: Blood glucose >250 mg/dL 1
- Metabolic acidosis: Venous pH <7.3 AND serum bicarbonate <15 mEq/L 1
- Ketosis: Elevated blood ketones, measured as β-hydroxybutyrate 1, 2
Critical Exception: Euglycemic DKA
Approximately 10% of DKA cases present with glucose <200 mg/dL (euglycemic DKA), particularly in patients taking SGLT2 inhibitors, during pregnancy, with alcohol use, or with reduced food intake 3. Do not dismiss DKA because glucose is <250 mg/dL—the diagnosis still requires acidosis and ketosis. 2
Severity Classification
Classify DKA severity immediately upon diagnosis 1:
- Mild: pH 7.25-7.30, bicarbonate 15-18 mEq/L, alert mental status 1
- Moderate: pH 7.00-7.24, bicarbonate 10-15 mEq/L, drowsy/lethargic 1
- Severe: pH <7.00, bicarbonate <10 mEq/L, stuporous or comatose 1
Severe DKA carries higher morbidity and mortality and requires intensive monitoring including central venous and intra-arterial pressure monitoring 1.
Essential Laboratory Workup
Obtain immediately upon presentation 1, 2:
- Complete metabolic panel (electrolytes, BUN, creatinine)
- Venous blood gas (pH, bicarbonate)
- Blood β-hydroxybutyrate (preferred ketone measurement)
- Complete blood count
- Urinalysis
- Serum osmolality
- Electrocardiogram
- Calculate anion gap: [Na⁺] - ([Cl⁻] + [HCO₃⁻]), should be >10-12 mEq/L in DKA 1
- Correct serum sodium for hyperglycemia: [measured Na] + [(glucose - 100)/100] × 1.6 1
If infection is suspected, obtain bacterial cultures of urine, blood, and throat 1.
Critical Ketone Measurement Pitfall
Never use urine ketones or nitroprusside-based tests for diagnosis or monitoring. 1, 2 These methods only measure acetoacetate and acetone, completely missing β-hydroxybutyrate (β-OHB)—the predominant and strongest ketoacid in DKA 1, 2. During treatment, β-OHB converts to acetoacetate, making nitroprusside tests paradoxically appear worse even as the patient improves 1.
Treatment of Diabetic Ketoacidosis
Fluid Resuscitation
Begin aggressive fluid resuscitation with isotonic saline at 15-20 mL/kg/hour immediately to restore circulatory volume and tissue perfusion. 1 Subsequent fluid choice depends on hydration state, serum electrolytes, and urine output 1. Total fluid replacement should correct estimated deficits within 24 hours, with careful monitoring for fluid overload in patients with renal or cardiac compromise 1.
Insulin Therapy
Start continuous IV regular insulin infusion at 0.1 units/kg/hour without an initial bolus 1. If glucose does not fall by 50 mg/dL in the first hour, double the insulin infusion rate hourly until achieving a steady decline of 50-75 mg/dL per hour 1.
When blood glucose falls below 200-250 mg/dL, add dextrose to IV fluids while continuing insulin infusion to clear ketones. 1, 3 This is critical—do not stop insulin therapy prematurely before ketoacidosis resolves, regardless of glucose levels. 3
Transition to Subcutaneous Insulin
Administer basal subcutaneous insulin 2-4 hours before stopping IV insulin to prevent rebound hyperglycemia 1. Patients on intensive insulin therapy should not stop or hold basal insulin even if not eating 3.
Potassium Replacement
If initial potassium is <3.3 mEq/L, delay insulin therapy and aggressively replace potassium first to prevent fatal cardiac arrhythmias. 1
Once serum potassium falls below 5.5 mEq/L and adequate urine output is confirmed, add 20-30 mEq potassium per liter of IV fluid to maintain serum potassium 4-5 mEq/L 1. Continue until the patient can tolerate oral supplementation 1.
Bicarbonate Therapy
Do not administer bicarbonate therapy except when pH <6.9. 1 Routine bicarbonate use is not recommended by the American Diabetes Association 1.
Monitoring During Treatment
Draw blood every 2-4 hours to measure 1, 2:
- Electrolytes
- Glucose
- Venous pH (arterial blood gases are unnecessary after initial diagnosis) 1
- β-hydroxybutyrate
- Anion gap
- BUN/creatinine
- Serum osmolality
After initial diagnosis, venous pH and anion gap adequately monitor acidosis resolution—do not repeat arterial sticks unnecessarily. 1 Venous pH is typically 0.03 units lower than arterial 1.
Resolution Criteria
DKA is resolved when ALL of the following are met 1, 2:
- Glucose <200 mg/dL
- Venous pH >7.3
- Serum bicarbonate ≥18 mEq/L
- Anion gap ≤12 mEq/L
Ketonemia typically takes longer to clear than hyperglycemia, requiring continued monitoring 1. Continue monitoring β-hydroxybutyrate until it normalizes 1.
Special Considerations
Monitor closely for cerebral edema during treatment, especially with overly aggressive fluid resuscitation, particularly in children 1. Failing to identify and treat the underlying precipitating cause of DKA can lead to recurrence. 1
Prevention and Patient Education
Provide education on recognition, prevention, and management of DKA to prevent recurrence 1. Individuals at risk should measure blood ketones when glucose levels exceed 200 mg/dL or in the presence of symptoms and potential precipitating factors 3. Blood β-hydroxybutyrate testing is superior to urine ketone testing for early detection, allowing earlier intervention and preventing progression to full DKA 1.