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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
Atomic absorption spectrometry (AAS) or colorimetric
Environmental exposure: 12.0−293.0 mg/24 hours
Hypercalcemia, hypophosphatemia and acidosis are among inhibitors of tubular reabsorption of magnesium.2
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.
Refrigerate (KBS tablet is acceptable).
Causes for Rejection
No preservative in the collection container; presence of blood in the urine; improper labeling
The test request form must state 24-hour collection volume. After collection, pH is adjusted to 1.5 to 2.0 with 6N HCl.
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|003400||Magnesium, Urine||013730||Magnesium, U||mg/dL||19124-7|
|003400||Magnesium, Urine||013805||Magnesium,Urine 24hr||mg/24 hr||24447-5|