A 26-year-old man with type 1 diabetes presents with vomiting and abdominal pain. Glucose is 480 mg/dL, pH 7.08, bicarbonate 6 mEq/L, serum potassium 2.9 mEq/L. IV fluids are being infused. What should be done about insulin therapy at this moment?
- A Start regular insulin infusion immediately at 0.1 units/kg/hour
- B Give a single intramuscular bolus of 0.1 units/kg regular insulin
- C Withhold insulin until potassium exceeds 3.3 mEq/L ✓
- D Start insulin only after the arterial pH rises above 7.2
Correct answer: C. Withhold insulin until potassium exceeds 3.3 mEq/L
Explanation
Insulin drives potassium into cells and can precipitate fatal hypokalaemia when the initial serum potassium is already low. ADA guidance is to delay the insulin infusion until potassium is above 3.3 mEq/L while replacing potassium concurrently. Fluids alone will lower glucose somewhat. Insulin is not delayed for pH correction, and bolus IM dosing is not standard practice here.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.