Potassium Deficit Calculator

About this calculator

Potassium deficit is a clinical estimate of the total amount of potassium, in milliequivalents (mEq), that a patient with hypokalemia (low blood potassium) needs replaced to bring their level back to normal, since serum potassium alone understates the true deficit — most of the body’s potassium is stored intracellularly, not in the blood that gets measured. Clinicians commonly use a rule-of-thumb estimate, such as roughly 200 to 400 mEq of total body deficit for each 1 mEq/L the serum level sits below normal, adjusted for the patient’s body weight.

This estimate guides how aggressively and over what timeframe potassium should be repleted — orally or intravenously — since correcting a large deficit too quickly, especially by IV, carries real cardiac risk from hyperkalemia and arrhythmia. It’s a clinical planning tool used alongside frequent lab monitoring, not a substitute for a clinician’s judgment on the underlying cause and repletion route.