Testing of urinary potassium levels can be prescribed for individuals to help find the cause of abnormal potassium levels in the blood (see your blood potassium results) or to help specify the cause of certain abnormal kidney function tests or to guide treatment. Results are expressed in millimoles of potassium per litre of urine (mmol/L) in a single urine specimen and in millimoles of potassium per day (mmol/d) in a 24-hour urine collection.
Urinary potassium (kaliuria) levels are interpreted in association with blood potassium levels. Normally, the body eliminates excess potassium, and high urinary potassium (hyperkaliuria) levels may result from blood levels that are too high (hyperkalemia). Hyperkaliuria can also be observed when the body loses too much potassium. In this case, blood potassium levels should be low or low-normal. Hyperkaliuria may result from kidney disease, eating disorders such as anorexia or muscle damage.
If blood potassium levels are lowered due to insufficient intake, urinary potassium levels should also be lower (hypokaliuria). Hypokaliuria may be caused by certain drugs such as non-steroidal anti-inflammatory drugs, beta-blockers, lithium, or lack of aldosterone secretion by the adrenal glands.