Potassium in urine 30 – 130 mmol/day
Potassium secretion in urine covaries with the intake through the diet. It is regulated by aldosterone and by direct effects of increased plasma concentraion of potassium. About 90 % of filtered potassium is reabsorbed in the proximal convoluted tubule and loop of Henle of the nephron. The remaining 10 % is subjected to regulated reabsorption or secretion, primarily in the aldosterone-sensitive principal cells in the distal tubules and proximal parts of the collecting ducts. Hyperkalemia stimulates the adrenal glands to increase secretion of aldosterone that again increase secretion of potassium and reabsorption of sodium in principal cells.
In a potassium deficiency, the secretion of potassium in the urine is reduced to 5 - 25 mmol/day. In a patient with hypokalemia, the secretion of < day of potassium indicates previous use of diuretics or extrarenal causes of potassium loss, for example diarrhoea. A patient with hypokalemia secreting > 25 mmol/day of potassium in the urine indicates the fall is partially renal related.
Read more about potassium secretion in the urine in The handbook on medical biochemistry