: Diabetic ketoacidosis (DKA) is one of the most serious complications of type 1 diabetes mellitus. Its treatment requires fluid and electrolyte replacement and insulin. Hypophosphatemia as a complication of treatment has been scarcely evaluated.

Objective: To estimate the incidence of hypophosphatemia in children with DKA, treated with subcutaneous regular insulin (IRS), and to explore factors associated with this complication.

Methods: Prospective, observational study. Patients diagnosed with DKA hospitalized in the general care ward were included. Data on phosphatemia, glycemia, acid-base status, and IRS amount (U/kg) received were recorded at baseline and after 24 h of treatment. Hypophosphatemia was defined as values below 2.5 mg/dl. The correlation between initial phosphate and at 24 h of treatment was evaluated; the incidence of hypophosphatemia at 24 h was expressed as a percentage of the total number of patients.

Results: 30 patients were included, 15 were female, mean age 11.4 ± 3.2 years. At 24 h of treatment with IRS, 36.7% (95%CI 22-55%) presented hypophosphatemia, mean value 1.9 ± 1.5 mg/dl. Initial bicarbonate < 10 mmol/L acted as a predictor of hypophosphatemia (OR 7.5; 95%CI 1.4-39.8%; p = 0.01). No patient required intravenous phosphate correction, and no associated clinical complications were observed.

Conclusions: In the group studied, the incidence of hypophosphatemia reached 36.7% at 24 hours of treatment. Initial bicarbonate lower than 10 mmol/L was significantly associated with hypophosphatemia. No complications associated with hypophosphatemia were observed.