Phosphorus, Serum Concentration (24-Hour Urine Collection)

Why This Test Is Done

Your healthcare provider may order this test if you have symptoms like muscle weakness, bone pain, or unexplained fatigue. It may also be used to monitor kidney disease, metabolic bone disorders, or conditions affecting phosphorus metabolism, such as hyperparathyroidism or certain cancers.

What to Expect Before the Test

You’ll need to collect all urine for 24 hours, starting after your first morning urine void. Store the urine in a clean container, keeping it refrigerated if possible. Bring the entire sample to your lab appointment. Follow any specific instructions your provider gives you to ensure accurate results.

What to Expect During the Test

A simple blood draw is performed to measure serum phosphorus levels. The 24-hour urine collection is done separately, requiring careful tracking of urine output throughout the day. No special preparation is needed beyond following the collection instructions.

What the Results Mean

Results help determine if your body is retaining or losing too much phosphorus. Abnormal levels may indicate kidney problems, metabolic disorders, or other health conditions that need further evaluation.