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Phosphorus Urine Test, 24-Hour

A Phosphorus Urine Test, 24-Hour is used to evaluate calcium/phosphorus balance.

Sample Report

Test Code: 003251

CPT Code: 84105

Also Known As: phosphate urine test; Urine Phos; Urine Phosphorus; PO4



Specimen Type: Urine


You must take your lab order to the lab to obtain a proper specimen container before collection. No fasting required. Urinate at 8am and discard the specimen. Then collect all urine in 24-hour period, ending with final collection at 8am the next morning. Refrigerate the collected urine between all voidings or keep it in a cool place. Screw the lid on securely. Transport the specimen promptly to the laboratory. Container must be labeled with full name, date and time collection started, and date and time collection finished.

Test Results:

2-3 days. May take longer based on weather, holiday or lab delays.


The phosphate urine test measures the amount of phosphate in a sample of urine collected over 24 hours (24-hour urine test). Phosphate is a charged particle (ion) that contains the mineral phosphorus. The body needs phosphorus to build and repair bones and teeth, help nerves function, and make muscles contract. Most (about 85%) of the phosphorus contained in phosphate is found in bones. The rest of it is stored in tissues throughout the body.

Urinary phosphorus concentration is useful to assess phosphorus balance. Thyroid and kidneys are key organs whose function influences urinary excretion. This test is also used to identify phosphorus as a possible cause of kidney stones. Many other medical conditions affect urinary phosphorus levels. High urine phosphate levels may be caused by kidney diseases, an overactive parathyroid gland, an too much vitamin D in the body. Low urine phosphate levels may be caused by an underactive parathyroid gland, kidney or liver diseases and malnutrition.


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