A 22-year-old man presents with 2 days of vomiting and abdominal pain. Blood glucose is 540 mg/dL, pH 7.08, bicarbonate 6 mEq/L, urine ketones strongly positive, and serum potassium 3.1 mEq/L. What is the correct next step in management?
- A Give intravenous regular insulin immediately and recheck potassium after 2 hours
- B Give sodium bicarbonate infusion to correct the acidosis before any other therapy
- C Add potassium to intravenous fluids and start insulin once potassium is above 3.3 mEq/L ✓
- D Start 0.45% saline at 250 mL/hour and hold all therapy until electrolytes normalize
Correct answer: C. Add potassium to intravenous fluids and start insulin once potassium is above 3.3 mEq/L
Explanation
Insulin drives potassium into cells and can precipitate fatal hypokalaemia when the admission value is already low. ADA guidance is to hold insulin until potassium exceeds 3.3 mEq/L and to replace potassium concurrently. Bicarbonate is reserved for pH below 6.9, so option B fails here. Isotonic saline, not half-strength, is the initial fluid.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.