Diagnostic Criteria for Diabetic Ketoacidosis (DKA)
DKA is diagnosed when all three of the following criteria are present: blood glucose >250 mg/dL (though this is being de-emphasized), pH <7.3 OR serum bicarbonate <18 mEq/L, and elevated serum or urine ketones with an anion gap >10 mEq/L 1, 2.
The Classic Triad
The traditional diagnostic approach requires:
- Hyperglycemia: Blood glucose >250 mg/dL
- Metabolic acidosis:
- pH <7.3 (venous pH acceptable, typically ~0.03 lower than arterial)
- Serum bicarbonate <18 mEq/L
- Anion gap >10 mEq/L
- Ketonemia or ketonuria: Elevated serum (preferred) or urine ketones 2
Critical Modern Update: Euglycemic DKA
Recent guidelines have de-emphasized the hyperglycemia requirement because of increasing euglycemic DKA (eDKA), particularly with SGLT2 inhibitor use 2. This means you can have DKA with normal or minimally elevated glucose levels. The diagnosis hinges on the presence of ketoacidosis, not just hyperglycemia 3.
Severity Classification
DKA severity is stratified based on:
- Mild DKA: pH 7.25-7.30, bicarbonate 15-18 mEq/L
- Moderate DKA: pH 7.0-7.24, bicarbonate 10-15 mEq/L
- Severe DKA: pH <7.0, bicarbonate <10 mEq/L, altered mental status, or severe dehydration 1
Essential Initial Laboratory Workup
When DKA is suspected, obtain immediately 1:
- Blood glucose (point-of-care and serum)
- Venous blood gas (arterial not necessary; venous pH adequate for monitoring)
- Complete metabolic panel: electrolytes, BUN, creatinine, calcium, phosphorus
- Serum ketones (β-hydroxybutyrate preferred over nitroprusside method)
- Urinalysis with ketones
- Anion gap calculation
Additional tests to consider based on clinical presentation: complete blood count, A1C, ECG, amylase/lipase, hepatic transaminases, troponin, blood/urine cultures, chest X-ray 2.
Important Caveats and Pitfalls
Do not rely on nitroprusside-based ketone testing to monitor treatment response 1. This method only measures acetoacetate and acetone, missing β-hydroxybutyrate (the predominant ketoacid in DKA). During treatment, β-hydroxybutyrate converts to acetoacetate, falsely suggesting worsening ketosis. Use serum β-hydroxybutyrate levels instead.
Clinical diagnosis may supersede laboratory criteria in real-world practice. One study found that 31% of patients diagnosed with DKA by emergency physicians did not meet strict laboratory criteria 4. Clinical features like Kussmaul breathing, altered mental status, and dehydration guide diagnosis when laboratory values are borderline or unavailable 5.
SGLT2 inhibitors modestly increase DKA risk, particularly eDKA, where glucose may be <250 mg/dL despite significant ketoacidosis 2. Maintain high clinical suspicion in patients on these medications presenting with nausea, vomiting, or abdominal pain.
Resolution Criteria
DKA is considered resolved when 1:
- Glucose <200 mg/dL
- Serum bicarbonate ≥18 mEq/L
- Venous pH ≥7.3
Monitor these parameters every 2-4 hours during treatment to assess response and adjust therapy accordingly.