University of Iowa
Diagnostic Laboratories
(UIDL) Test Directory

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Magnesium
Order Code: MG
Order Form: Laboratory Requisition
Specimen:
Plasma
Collection Medium:
Plasma separator tube
Alternate
Collection Media:
Call laboratory for additional acceptable specimen collection 
containers.
Minimum:
2 mL whole blood in light green top tube or 2 microtubes for pediatric 
patients
Rejection Criteria:
Avoid hemolysis
Testing
Schedule:
24 hrs/day, 7 days a week, including holidays.
Analytic Time:
2 hours (upon receipt in laboratory)
Reference Range:
1.5-2.9 mg/dl

Critical value: <1.0 mg/dl and >4.7 mg/dl
Comments:
Avoid hemolysis.

Please print, complete and submit the Advance Beneficiary Notice 
(ABN) along with the Laboratory Requisition before shipping the 
specimen.
Test
Limitations:
Criterion: Recovery within plus or minus 10% of initial values

Plasma
Icterus: No significant interference up to an I index of 65 (conjugated 
bilirubin) and an I index of 37 (unconjugated bilirubin) corresponding 
to an approximate bilirubin concentration of 65 mg/dl (conjugated) and 
37 mg/dl (unconjugated).

Hemolysis interferes due to magnesium released from erythrocytes.

Lipemia (Intralipid): No significant interference up to an L index of 
400 (approximate triglycerides concentration: 800 mg/dl). There is poor 
correlation between turbidity and triglycerides concentration.

In-vitro tests were performed on 34 commonly used pharmaceuticals.

No interference with the assay was found.

Reference:
Glick MR, Ryder KW, Jackson SA. Graphical Comparisons of Interferences 
in Clinical Chemistry Instrumentation. Clin Chem 1986;32:470-474.
Methodology:
Colormetric endpoint
Sample
Processing:
Centrifuge at 3000 RPM for 10 minutes.
Aliquot plasma into labeled container and cap.
Sample
Storage:
Refrigerate.
Transport
Instructions:
Place requisition into outside pocket of bag.
Place specimen into zip-lock type bag, seal bag.
Transport in cooler with refrigerated coolant packs.
CPT Code:
83735
 
See Additional Information:
Chemistry Critical Lab Values

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Updated: 09/13/2007