A 10-year-old girl in diabetic ketoacidosis has blood glucose 900 mg/dL and measured serum sodium 130 mEq/L. What is her corrected serum sodium?

• A 130 mEq/L, glucose does not affect sodium measurement
• B Approximately 138 mEq/L
• C Approximately 122 mEq/L
• D Approximately 143 mEq/L ✓

Explanation

Hyperglycemia draws water into the extracellular space and dilutes sodium. The standard correction adds 1.6 mEq/L to the measured sodium for every 100 mg/dL of glucose above 100 mg/dL. Here glucose exceeds normal by 800 mg/dL, giving 1.6 times 8, about 13, so corrected sodium is roughly 143 mEq/L. This matters because it reveals hypertonic dehydration despite a low measured value. A corrected sodium below normal would suggest genuine sodium loss, while 122 mEq/L is arithmetically wrong in direction.

Reference: Nelson Textbook of Pediatrics, 21st ed.

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