A 24-year-old man presents with diabetic ketoacidosis: glucose 520 mg/dL, pH 7.12, bicarbonate 8 mEq/L. Initial serum potassium is 3.0 mEq/L. What is the correct approach to insulin therapy?

• A Start regular insulin IV at 0.1 U/kg/hour immediately along with potassium infusion
• B Withhold insulin until serum potassium exceeds 3.3 mEq/L ✓
• C Give a single subcutaneous glargine dose and reassess in 6 hours
• D Start insulin only after the anion gap has narrowed

Explanation

In DKA, insulin drives potassium into cells and precipitates fatal hypokalaemia when the initial level is already low. Standard teaching (Harrison, ADA guidance) is to delay insulin until potassium rises above 3.3 mEq/L while replacing potassium in saline. Option A is the classic error: insulin must never be started before potassium correction at this level. Once potassium exceeds 3.3 mEq/L, IV regular insulin 0.1 U/kg/hour is begun.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.