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Test Code NBLD0176 Magnesium, 24 Hour Urine

Useful For

  • Assessing the cause of abnormal serum magnesium concentrations
  • Determining whether nutritional magnesium loads are adequate
  • Assessing kidney stone risk


Colorimetric Methylthymol Blue (MTB)/Bichromatic End point

Performing Laboratory

Bozeman Health Laboratory Services

Specimen Requirements

Specimen Type: Urine
Container/Tube: 24-hour urine collection container
Specimen Volume:

Preferred: 10 mL

Acceptable: Entire collection
Specimen Minimum Volume: 1 mL
Collection Instructions:
1. Collect a 24-hour urine specimen.

2. No preservative required.

3. Refrigerate specimen during collection.

4. Mix well before taking aliquot.

Additional Information:

1. Starting and ending times of collection are required.

2. Follow special collection instructions below.

Special Instructions

Specimen Transport Temperature


Specimen Stability


Specimen Type Temperature Time
Urine Ambient 7 days
  Refrigerated 7 days


Reference Values

24.0-255.0 mg/24 hours

Day(s) Test Set Up

Monday through Sunday

Test Classification and CPT Coding


81050-Urine timed measurement (if appropriate)