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Magnesium, Serum / Plasma

Item Value
Test Update Information Effective 11/27/12, the magnesium reagent has been restandardized to the NIST standard 956 L1 causing results to decrease by 0.1 mg/dL
Approval req'd? No
Available Stat? Yes
Test code MG
Test group Magnesium
Performed by Parnassus & Mt. Zion Chemistry
In House Availability Test available 24 hours per day 7 days per week
Method Spectrophotometric (calmagite dye)
Container type Gold top or Light Green top
Amount to Collect 1 mL blood Click here for Microdetermination info
Sample type Serum or plasma
Preferred volume 0.5 mL serum or plasma
Min. Volume 0.2 mL serum or plasma Click here for Microdetermination info
Units mg/dL
Normal range 1.8 - 2.4 mg/dL

Normal range was determined by testing 271 male and female adult healthy blood donors at UCSF. Pediatric patients will use adult range due to comparable ranges between UCSF's normal study and Soldin, Steven J. Pediatric Reference Intervals, 6th edition, AACC Press, 2007.
Critical value
Most Units < 1.0 mg/dL or > 4.5 mg/dL
Birth Center < 1.0 mg/dL or > 8.0 mg/dL
Synonyms Mg
Stability Room temperature 8 hours, refrigerated 2 days, frozen at -20C 1 week
Turn around times STAT 1 hour, Routine 4 hours
Additional information To convert mg/dL to mmol/L (SI units) multiply by x 0.411.

Severely lipemic samples will be treated and reassayed. Hemolysis may artifactually increase the result.

Gadolinium MR contrast agents including Gadodiamide (Omniscan), Gadoversetamide (Optimark), Gadopentetate Dimeglumine (Magnevist), and Gadoterdiol (Prohance), have been shown to interfere with certain colorimetric assays used in the measurement of various serum cations including iron,
magnesium, and calcium. The UCSF clinical labs utilize a colorimetric assay for the measurement of both serum iron and serum magnesium that are subject to this interference. For serum magnesium, some gadolinium containing agents (Gadodiamide and Gadoversetamide) may produce a falsely elevated result (on average 117 and 124% respectively, of the true serum magnesium
concentration). See "Calcium" and "Iron" entries for respective interferences.

Reference:Proctor et al. Gadolinium Magnetic Resonance contrast Agents produce Analytic Interference in Multiple Serum Assays. Am J Clin Pathol. 2004;121:282-292.
CPT coding 83735
Medical Necessity? Yes. Click here for more information
LOINC code 19123-9
Last Updated 10/15/2014 11:48:16 AM
Entry Number 637
Lab Procedure Link Click here for Procedure
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