A 24-year-old man with new-onset type 1 diabetes presents with glucose 620 mg/dL, pH 7.12, bicarbonate 8 mEq/L, and serum potassium of 3.0 mEq/L. IV fluids are being started. What is the correct next step regarding potassium before initiating insulin?

• A Start insulin infusion immediately; add potassium once urine output is established
• B Start insulin and give sodium bicarbonate simultaneously to correct acidosis
• C Withhold all potassium until the anion gap normalises
• D Give 20 to 30 mEq/L of potassium per hour until serum potassium exceeds 3.3 mEq/L, then start insulin ✓

Explanation

Insulin drives potassium intracellularly, so giving insulin with a serum potassium below 3.3 mEq/L risks fatal hypokalaemia and arrhythmia. Standard DKA protocols (ADA, Harrison) require replacing potassium first and deferring insulin until potassium is above 3.3 mEq/L. Bicarbonate is not indicated at this pH unless it falls below 6.9, and it does not address the potassium risk.

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

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Written and medically reviewed by the StethoPrep medical team.