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Test Code 293 Magnesium

Important Note

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

Additional Codes


PowerChart: Magnesium Level

MA Cerner: Magnesium Level.

Specimen Requirement

0.5 mL serum or plasma is required.

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.

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.


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.

CPT Code Information

83735 Chemistry: Magnesium

LOINC Code Information

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

Test Method

MercyOne: Timed Endpoint Method; Beckman DXC880i

MA: Enzymatic Colorimetric Method; Roche Cobas 6000

Reference Values

1.6-3.0 mg/dL

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