Special Instructions
The test request form must state 24-hour collection volume. After collection, pH is adjusted to 1.5 to 2.0 with 6N HCl.
Expected Turnaround Time
1 - 3 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Related Information
Related Documents
Specimen Requirements
Specimen
Urine (24-hour)
Volume
5 mL
Minimum Volume
2.2 mL (Note: This volume does not allow for repeat testing.)
Container
Plastic urine container with 30 mL 6N HCl
Collection
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.
Storage Instructions
Room temperature (KBS tablet is acceptable)
Stability Requirements
Temperature | Period |
|---|---|
Room temperature | 14 days |
Refrigerated | 14 days |
Frozen | 14 days |
Freeze/thaw cycles | Stable x3 |
Causes for Rejection
No preservative in the collection container; presence of blood in the urine; improper labeling
Test Details
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
Methodology
Atomic absorption spectrometry (AAS) or colorimetric
Reference Interval
Environmental exposure: 12.0−293.0 mg/24 hours
Additional Information
Hypercalcemia, hypophosphatemia and acidosis are among inhibitors of tubular reabsorption of magnesium.2
Footnotes
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 003400 | Magnesium, Urine | 19124-7 | 013732 | Magnesium, U | mg/dL | 19124-7 |
| 003400 | Magnesium, Urine | 19124-7 | 013806 | Magnesium,Urine 24hr | mg/24 hr | 24447-5 |
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