In a patient with serum glucose 390 mg/dL, anion gap 12, and bicarbonate (CO₂) 25 mmol/L, does this indicate diabetic ketoacidosis or hyperosmolar hyperglycemic state, and is the patient's mental status normal?

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Last updated: September 13, 2026 • View editorial policy

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This is NOT DKA

Based on the laboratory values provided—glucose 390 mg/dL, anion gap 12, and bicarbonate (CO₂) 25 mmol/L with normal mentation—this patient does NOT meet criteria for either diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS). This represents uncomplicated hyperglycemia that requires treatment but not as an acute hyperglycemic crisis.

Why This is Not DKA

The diagnostic criteria for DKA are clear and this patient fails to meet them 1:

  • Anion gap requirement: DKA requires anion gap >10 (mild) to >12 (moderate/severe). This patient has AG = 12, which is at the threshold but...
  • Bicarbonate requirement: DKA requires bicarbonate <15-18 mEq/L depending on severity. This patient has CO₂ = 25 mEq/L, which is normal
  • pH requirement: DKA requires arterial pH <7.3. With a normal bicarbonate of 25, the pH is almost certainly normal
  • Ketones: DKA requires positive ketones (not provided in your case, but unlikely given normal bicarbonate)

The American Diabetes Association guidelines are explicit: DKA diagnosis requires blood glucose >250 mg/dL AND arterial pH <7.3 AND bicarbonate <15 mEq/L AND moderate ketonuria or ketonemia 1. Your patient only meets the glucose criterion.

Why This is Not HHS

HHS also does not fit 1:

  • Glucose requirement: HHS typically requires glucose >600 mg/dL. This patient has 390 mg/dL
  • Osmolality requirement: HHS requires effective serum osmolality >320 mOsm/kg. Calculate: 2[Na] + (390/18) = 2[Na] + 21.7. Unless sodium is severely elevated (>149), osmolality won't reach 320
  • Mental status: HHS characteristically presents with stupor/coma. This patient has normal mentation

What You're Actually Dealing With

This is simple hyperglycemia in a diabetic patient, likely from:

  • Medication non-adherence
  • Intercurrent illness without metabolic decompensation
  • Inadequate insulin dosing
  • New-onset diabetes

Immediate Management Approach

  1. Check urine or serum ketones to definitively rule out early/resolving DKA
  2. Calculate effective osmolality: 2[measured Na] + (glucose/18) to assess hydration status
  3. Assess for precipitating factors: infection, MI, medication changes
  4. Treat with subcutaneous insulin if patient is eating and hemodynamically stable—no need for IV insulin or ICU admission 2
  5. Provide hydration if clinically dehydrated, but this doesn't require the aggressive 15-20 mL/kg/h used in DKA 1

Critical Pitfall to Avoid

Do not over-treat this as DKA. The normal bicarbonate and anion gap at threshold tell you there is no significant ketoacidosis or metabolic acidosis. Treating with DKA protocols (aggressive IV fluids, continuous insulin infusion, ICU admission) would be inappropriate and potentially harmful, risking hypoglycemia and unnecessary resource utilization 3.

The preserved mental status with this glucose level further confirms this is not a hyperglycemic crisis—patients with HHS at similar or higher glucose levels typically have altered consciousness 1.

References

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