A 24-year-old man with type 1 diabetes presents with vomiting, abdominal pain, and Kussmaul breathing. Glucose is 540 mg/dL, pH 7.08, bicarbonate 6 mEq/L, ketones strongly positive. After starting IV fluids, his serum potassium is reported as 3.1 mEq/L. Which is the correct next step regarding insulin therapy?

• A Start regular insulin IV infusion immediately at 0.1 units/kg/hour
• B Start sodium bicarbonate infusion before any insulin
• C Give subcutaneous glargine along with the IV infusion
• D Delay insulin infusion and begin potassium replacement first, restarting insulin once potassium exceeds 3.3 mEq/L ✓

Explanation

Insulin drives potassium into cells and can drop a level of 3.1 mEq/L into life-threatening hypokalaemia with arrhythmia. Standard DKA protocols (ADA, JBDS) state that if potassium is below 3.3 mEq/L, insulin must be withheld while potassium is replaced, and the infusion started only once the level exceeds 3.3 mEq/L. Bicarbonate is reserved for pH below about 6.9, so option B is wrong, and this patient's acidosis alone does not mandate it.

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

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Written and medically reviewed by the StethoPrep medical team.