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The University of Chicago Medicine Laboratories

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Specimen Collection and Handling

Transfusion

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Mayo Clinic Laboratories

Test Code MG Magnesium

Specimen and Container/Tube

Specimen Type: Plasma

Preferred Specimen: Li-Heparin Mint Green Top

Other Acceptable specimens: Serum/Gold Top, Serum/Red Top

Specimen Stability

Storage Temperature

Stability

Room Temperature

7 days

Refrigerated

7 days

Frozen

1 year

Collection Instructions

Collect specimen per standard laboratory collection procedures. 

 

Specimen Handling and Transport Instructions

UCMC Onsite Instructions: 

  • Collect specimen per standard collection procedure and send to laboratory immediately. 

 

UCMC Offsite and UC MedLab Outreach Instructions: 

  • Samples should be centrifuged within 2 hours of collection.
  • Centrifuge specimens at >2500 x g for 10 minutes at room temperature.
  • Aliquot sample into plastic transport tube containing a minimum of 0.2 mL of specimen.
  • Samples must be sent room temperature at 20-25oC.

Rejection Criteria

  • Common specimen rejected situations include: incorrect specimen type, insufficient volume, missing or incomplete specimen identifiers, incorrect specimen transport, or specimens outside stability limits. 
  • Specimens that are clotted or grossly hemolyzed.
  • Specimens that were transported unspun/whole blood and draw time is greater than 6 hours

Reference Values

Test

Age

Sex

Reference Range

Magnesium 

All

All

1.6 - 2.5 mg/dL

Critical Values

Analyte

Unit

Low

High

Age

Magnesium 

mg/dL

< 1.0

> 8.0

N/A

Turnaround Time

Turnaround times are relative to the time the specimen is received in the test laboratory. 

 

STAT Turnaround Time: 1 hour

Routine Turnaround Time: up to 4 hours

Testing Schedule:  24/7

Clinical Indications

This assay is used for diagnosing and monitoring hypomagnesemia (magnesium deficiency) and hypermagnesemia (magnesium excess).

Test Components

Magnesium

Methodology

Colormetric endpoint method (Roche Diagnostics)

CPT Codes

83735

LOINC Codes

19123-9

Synonyms/Keyword Search

N/A

Additional Information

  • Results should always be assessed in conjunction with patient's medical history, clinical examination and other findings.

Last Review Date

3/19/25

Volume

Preferred Volume: 0.5 mL

Minimum Volume: 0.2 mL