Hypokalemia laboratory tests

; Associate Editor-In-Chief: ; Assistant Editor(s)-In-Chief: Jack Khouri

Laboratory Findings

 * Complete blood count (CBC)
 * Blood urea nitrogen (BUN)/creatinine
 * Calcium
 * Magnesium
 * Glucose
 * Arterial blood gases
 * Aldosterone level
 * Renin levels
 * Urinary sodium
 * Urine potassium
 * Levels <25 meq/day (or <15 meq/L on urine spot) rule out a renal cause of hypokalemia and suggest extrarenal potassium loss or transcellular shift
 * Higher potassium excretion suggest renal losses.
 * Transtubular potassium gradient (TTKG)
 * TTKG= (Urine K x Plasma osmolarity)/(Plasma K x Urine osmolarity)
 * A TTKG less than 2-3 indicates renal potassium conservation in a hypokalemic patient
 * A urine osmolality less than plasma osmolality or urine sodium <20 mEq/L, the formula is not applicable
 * Urine chloride
 * <25 meq/L: vomiting or remote diuretic use
 * >40 meq/L: diuretics, Bartter's, Gitelman's and mineralocorticoid excess