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Test Code UMG24 Magnesium, Urine, 24 Hour, LAB406


Colorimetric (Dye-Methylthymol Blue)

Performing Laboratory

St. Luke's Hospital Cedar Rapids

Specimen Requirements


Preferred: 24-hour urine collection

Specimen Volume: 0.5 mL from a 24-hour timed urine collection. Add 10 mL of

                                 12M hydrochloric acid as preservative at start of collection. Refrigerate specimen

                                 during collection, and send specimen refrigerated.

Stability: Urine specimens for magnesium may be stored up to 7 days at 2-8°C. 

Collection Instructions: Obtain 24-hour urine jug from laboratory

Note: 1. Alternatively, specimen may be just refrigerated during collection, and acidified

               to a pH of <3 upon receipt in laboratory.

          2. Starting and ending times of collection are required for processing.

          3. When a 24-hour urine for Magnesium is done, a PV (period and volume) must also

               be ordered and resulted. (FOR LAB USE ONLY)

Reference Values

12.0-292.0 mg/24 hours

Day(s) Test Set Up

Monday through Sunday

Test Classification and CPT Coding

81050-Timed urine measurement


Useful For

Renal clearance plays a large role in magnesium homeostasis.  The determination of urinary magnesium is useful in estimating the rate of magnesium excretion.

Report Available

Within 1 hour of receipt