Specimen Requirements


Phosphorus, 24 Hour Urine

Specimen Requirement

Begin collecting at 8a.m., discarding the first sample. Then collect all urine including the final specimen voided at the end of the 24-hour urine collection period (i.e. 8a.m. the next morning). Note the total volume of the urine, mix well, then aliquot 10 mL into a sterile screw top urine container. Indicate the total volume of the urine on the sample or the requisition.




Room temp: 14 days, Refrigerated: 14 days, Frozen: 14 days

Reference Range

By Report*


1-2 days

Clinical Use

Evaluate calcium/phosphorus balance.

High urinary phosphorus (ie, increased renal losses) occurs in primary hyperparathyroidism, vitamin D deficiency, renal tubular acidosis, diuretic use. Phosphates are among the substances which may be lost in the Fanconi syndrome. Renal loss of phosphate may itself lead to rickets or osteomalacia.

Low in hypoparathyroidism, pseudohypoparathyroidism, vitamin D intoxication.

Evaluate nephrolithiasis. Hypophosphatemia with normal serum calcium, high alkaline phosphatase, hypercalciuria, low urinary phosphorus occur with osteomalacia from excessive antacid ingestion.

Test Code