Magnesium, Urine

Casandra

Casandra Test Code LC06011Version 1 (DRAFT)

Performing Lab

Lab LabcorpLab Test ID 003400CPT Code 83735

Clinical Use

Use

Magnesium excretion controls magnesium balance.1 Magnesium urinary excretion is enhanced by increasing blood alcohol levels, diuretics, Bartter syndrome, corticosteroids, cis-platinum therapy and aldosterone. Renal magnesium wasting occurs in renal transplant recipients who are on cyclosporine and prednisone.2 Renal conservation of magnesium is diminished by hypercalciuria, salt-losing conditions, and the syndrome of inappropriate secretion of antidiuretic hormone.1 Magnesium deficiency is often inadequately documented by serum magnesium levels. Urinary magnesium analyses have been advocated before and after therapeutic magnesium administration to further investigate the significance of an apparent low serum magnesium.3

Special Instructions

Not provided.

Limitations

The test may be affected by improper collection or transportation of the urine sample. The presence of blood in the urine, absence of preservative in the collection container, or improper labeling can lead to sample rejection. In addition, factors such as hypercalcemia, hypophosphatemia, and acidosis can interfere with the tubular reabsorption of magnesium, potentially impacting the results.

Test Details

Methodology

Other

Biomarkers

Magnesium

Analyte

Magnesium, U

Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Magnesium, Urine 24hr

Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

LOINC Codes

Order Codes

19124-7 - Magnesium Ur-mCnc

Result Codes

19124-7 - Magnesium Ur-mCnc
24447-5 - Magnesium 24h Ur-mRate

Result Turnaround Time

1-3 days

Specimen

Urine

Volume

5 mL

Minimum Volume

2.2 mL

Container

Plastic urine container with 30 mL 6N HCl

Collection Instructions

Instruct the patient to void at 8 AM and discard the specimen. Then collect all urine including the final specimen voided at the end of the 24-hour collection period (ie, 8 AM the next morning). Screw the lid on securely. Transport the specimen promptly to the laboratory. Container must be labeled with patient's full name, room number, date and time collection started, and date and time collection finished.