A 28-year-old woman with known type 1 diabetes presents in DKA. ABG: pH 7.12, PCO2 22 mmHg, HCO3 8 mEq/L. Serum glucose 480 mg/dL, Na 128 mEq/L, K 5.8 mEq/L. The corrected serum sodium = 128 + [(480 − 100)/100 × 1.6] = 128 + (3.8 × 1.6) = 128 + 6.1 = 134.1 mEq/L. Regarding initial potassium management, what is the threshold serum K below which IV potassium replacement must be given BEFORE starting insulin?

• A Potassium <3.5 mEq/L ✓
• B Potassium <5.0 mEq/L
• C Potassium <4.0 mEq/L
• D Potassium <3.0 mEq/L

Explanation

In DKA management, insulin must be withheld until serum potassium is confirmed ≥3.5 mEq/L, because insulin drives potassium intracellularly and can precipitate life-threatening hypokalemia and cardiac arrhythmias. If K is <3.5 mEq/L, IV potassium (20–40 mEq/hour) should be administered first. If K is 3.5–5.0 mEq/L, add potassium (20–30 mEq/L) to IV fluids concurrently with insulin. If K is >5.5 mEq/L (as in this patient), delay potassium supplementation and recheck in 1–2 hours.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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