A child with type 1 diabetes mellitus has been diagnosed with ketoacidosis. What laboratory finding is consistent with this diagnosis?

Rationale: A. Hemoglobin A1c of 5.5% is within the normal range and does not indicate chronic hyperglycemia or diabetic ketoacidosis (DKA). B. A fasting blood glucose of 124 mg/dL is elevated but not high enough to indicate DKA, which usually involves glucose levels >250 mg/dL. C. A serum pH of 7.24 indicates metabolic acidosis, a hallmark of diabetic ketoacidosis. This acidic state results from the buildup of ketones due to insulin deficiency. D. Potassium may initially be elevated in DKA due to acidosis, but a value of 3.9 mEq/L is within normal limits and not specific to DKA.