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Test Code MG Magnesium LAB103

Important Note

Some gadolinium magnetic resonance contrast agents may interfere with this assay.

Test Method

Timed Endpoint Method; Beckman DXC600


Testing is performed Monday through Sunday.

Routine: Typically completed within 4 hours after the
specimen arrives at the testing site.

Expedite: Typically completed within 1 hour after the
specimen arrives at the testing site.

STAT: Typically completed within 30 minutes after the specimen
arrives at the testing site.

Useful For

Monitoring preeclampsia patients being treated with magnesium
sulfate, although in most cases monitoring clinical signs
(respiratory rate and deep tendon reflexes) is adequate and blood
magnesium levels are not required.

Specimen Requirement

0.5 mL serum or plasma is required.

CPT Code Information

83735 Chemistry: Magnesium

Reference Values

1.6-3.0 mg/dL

  • Critical Value:

    • Low: < 1.0 mg/dL
    • High: > 4.0 mg/dL

LOINC Code Information

19123-9 Magnesium [Mass/Volume] In Serum Or Plasma

Additional Specimen Collection Information

Collect blood in a lithium heparin, green-top or red-top tube.
PST and SST (gel tubes) are acceptable. Serum or plasma should be
separated from contact with the cells within 2 hours of collection.
Specimens not centrifuged within 4 hours of collection may be
rejected. Refrigerate the specimen if unable to assay within 8
hours of collection. Hemolyzed specimens are not acceptable.
Samples with >2+ lipemia must be cleared prior to analysis.