Phosphorus, Urine

Urine Phosphorus, PO424, PHOSU

Test Codes

24-Hour Urine: EPIC: LAB426, Random Urine: EPIC: LAB427

Department

Chemistry

Instructions

NOTE: 24-hour and random urine specimens MUST be collected separately. See below for collection criteria.

• Please refer to the Specimen Collection Manual for instructions on 24-Hour or Random Urine Collection:
  • Urine 24-Hour Collection - Inpatient.
  • Urine 24-Hour Collection - Outpatient.
  • Urine 24-Hour Collection - Outreach.
  • Random Urine Collection.

Specimen Collection Criteria

Collect: 24-hour urine or timed urine specimen with a 24-hour urine container with 15 mL of 6N Hydrochloric Acid added prior to the start of collection.
Also acceptable: Random urine specimen in a screw-capped container or another sterile collection cup with no preservative (Minimum: 30 mL)

• Refer to the table of Urine Preservative Options when multiple tests are requested.
• Keep 24-hour urine specimen iced or refrigerated during collection.
• Include start and end dates and times for the collection period on the specimen container.

Urine Preservative Options
No Preservative	6N Hydrochloric Acid	Boric Acid (10g)	Sodium Carbonate	50% Acetic Acid
Acceptable	Preferred	Acceptable	Unacceptable	Unacceptable

Physician Office/Draw Specimen Preparation

Maintain specimens refrigerated (2-8°C or 36-46°F) prior to transport.

Preparation for Courier Transport

Transport: Entire 24-hour urine collection, or random urine, refrigerated (2-8°C or 36-46°F).

Rejection Criteria

Specimens not collected and processed as indicated. 

In-Lab Processing

Measure total volume of 24-hour urine specimen. Record total volume and collection start and end dates and times in the LIS system. Aliquot a minimum of 10 mL from the well-mixed 24-hour urine collection.

Storage

Specimen Stability for Testing:

Room temperature (20-26°C or 68-78.8°F): 4 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): For longer storage.

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 5 days (Royal Oak and Troy store an aliquot for 30 days.)

Laboratory

Dearborn Chemistry Laboratory
Troy Chemistry Laboratory
Royal Oak Automated Chemistry Laboratory
Grosse Pointe Chemistry Laboratory
Farmington Hills Chemistry Laboratory

Performed

Sunday – Saturday.
Results available within 24 hours.

Reference Range

Urine Phosphorus: 0.3 – 1.3 g/24 hours.
Normal ranges for random urines or for collections other than 24 hours have not been established.

Test Methodology

Spectrophotometry.

Interpretation

• Increased urine phosphorus levels are associated with hyperparathyroidism, vitamin D-resistant rickets, immobilization following paraplegia or fracture, vitamin D intoxication, renal tubular damage, familial hypophosphatemia, and nonrenal acidosis.
• Decreased levels are associated with hypoparathyroidism, pseudohypoparathyroidism, and parathyroidectomy.

Clinical Utility

Inorganic phosphorus measurements aid in the diagnosis and management of various disorders, including parathyroid gland and kidney diseases, vitamin D imbalance and kidney stones.

CPT Codes

84105

Contacts

Last Updated

8/1/2025