A 24-year-old man with type 1 diabetes presents with diabetic ketoacidosis: glucose 540 mg/dL, pH 7.08, bicarbonate 6 mEq/L, serum potassium 3.1 mEq/L. IV fluids and insulin infusion are being started. What is the correct approach to potassium?
- A Withhold all potassium until the repeat value after 1 hour of insulin
- B Give a bolus of 40 mEq potassium chloride intravenously over 10 minutes
- C Add 20 to 30 mEq of potassium per litre of fluid immediately, before insulin if urine output is adequate ✓
- D Delay potassium until serum potassium falls below 3.0 mEq/L
Correct answer: C. Add 20 to 30 mEq of potassium per litre of fluid immediately, before insulin if urine output is adequate
Explanation
Insulin drives potassium into cells and can precipitate fatal hypokalaemia. In DKA, potassium is added once serum potassium is below about 5.0 to 5.2 mEq/L and the patient is passing urine; a level of 3.1 mEq/L mandates immediate replacement, ideally before or with the insulin infusion. Withholding until a lower value (option D) risks arrhythmia, and waiting an hour wastes the window during which insulin will further lower potassium.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.