Why would a person need a urine phosphorus measurement?

Rare kidney problems. Phosphorus is an important compound that allows our muscles to contract, our nerves to function, and builds bones and teeth. Certain kidney problems can cause loss of phosphorous in the form of the ion phosphate, called hypophosphatemia. The phosphate urine test measures the amount of phosphate in a sample of urine collected over 24 hours (24-hour urine test).