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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: Magnesium, Urine, 24 hour

Test Code(s): UMG / HCUMG

CPT Code(s): 83735

Methodology: Methylthymol Blue

Days Performed: Daily, 24 hours.

Turnaround Time: Stat: 2 hours.
Routine: 4 hours.

Specimen Requirements

Specimen: 24 hour timed urine

Collection Instructions: Timed urine collection accepted.  No preservative necessary. For timed urine collections, collect all urine in container provided.  Add "Refrigerate" sticker to 24-hour container.

For 24-hour urine test the collection period must be within 22-26 hours.  Collection period starts after first void of the period.  It is very important to refrigerate specimen during and after the collection.  Indicate the date and time collection started and date and time collection finished.  If questions about collection process or container does not have instructions attached, call (608) 263-7060 for assistance.

Patient instructions available at Search for 24-hour urine collection or UWH#4339.

Collection Container: Preferred: 24 hour urine container

Collection Volume: Preferred: Entire collection
Pediatrics: Entire collection

Sample Analyzed: Urine aliquot

Volume Required: Preferred: 0.5 mL
Pediatrics: 0.2 mL

Specimen Transport: Transport entire specimen to UWHC Core Laboratory (B4/220) at close of collection.  Transport with coolant pack if coming from outreach location.

Outreach Specimen Transport: Mix urine well and note volume and period. Acidify with 6 N HCl to a pH of 2-3.   A pH lower than 2 may cause assay interference. Mix well and let stand for one hour.  Recheck pH. Transport  50 mL acidified aliquot with coolant pack to UWHC Core Laboratory (B4/220) along with volume and period information.

Stability: Ambient: 5 days
Refrigerated: 5 days


Reference Interval:

Age 18 years and up: 6-10 meq/24 hours


Results calculated only for collections of 22-26 hours.

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