In diabetic ketoacidosis management, why is potassium checked before starting insulin therapy?

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In diabetic ketoacidosis, insulin therapy shifts potassium from the extracellular space into cells, which can cause the serum potassium to fall rapidly. At the same time, many patients have a total body potassium deficit from osmotic diuresis and vomiting, even if the initial serum level appears normal or high. Starting insulin without addressing potassium can therefore precipitate severe hypokalemia and increase the risk of life-threatening arrhythmias. That’s why potassium is checked before giving insulin and corrected as needed: if potassium is very low, insulin is withheld until potassium rises to a safer level; if it’s in the mid-range, insulin is started with concurrent potassium replacement to keep levels in a safer range; if potassium is high, insulin can be started with careful monitoring and planned repletion to prevent a dangerous drop. Throughout insulin therapy, potassium is monitored frequently because shifts continue as acidosis resolves and glucose is corrected.