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Test ID MG_F Magnesium, Feces

Ordering Guidance

This test is only clinically valid if performed on watery specimens. In the event a formed fecal specimen is submitted, the test will not be performed.

Specimen Required

Patient Preparation: No barium, laxatives, or enemas may be used for 96 hours prior to start of, or during, collection.

Supplies: Stool containers - 24, 48, 72 Hour Kit (T291)

Container/Tube: Stool container

Specimen Volume: 10 g

Collection Instructions: Collect a very liquid stool specimen.

Useful For

Workup of cases of chronic diarrhea


Identifying the use of magnesium-containing laxatives contributing to osmotic diarrhea

Method Name

Colorimetric Titration

Reporting Name

Magnesium, F

Specimen Type


Specimen Minimum Volume

5 g

Specimen Stability Information

Specimen Type Temperature Time Special Container
Fecal Frozen (preferred) 14 days
  Refrigerated  7 days
  Ambient  48 hours

Reference Values

An interpretive report will be provided

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
MG_F Magnesium, F 29911-5


Result ID Test Result Name Result LOINC Value
MG_F Magnesium, F 29911-5

Day(s) Performed

Monday, Thursday

Report Available

1 to 3 days