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Test Code LAB104 Magnesium, Red Blood Cell

Important Note

This test will be discontinued January 1, 2019.

See Lab News for more information

Additional Codes

Mayo Code: FMAGR

Epic: LAB 104

Interface Order Alias: 11565

Cerner: 8196

Performing Laboratory

Medtox Laboratories, Inc.

Reporting Name

Magnesium, RBC

Specimen Type

Metal Free EDTA Plasma

Specimen Required

Collect whole blood from a metal-free EDTA (royal blue top) tube. Spin down and separate plasma and red blood cells immediately. Ship 2 mL plasma and 2 mL RBC in metal-free tubes, refrigerate.


NOTE: Both plasma and RBCs are required for testing.

Laboratory Test Directory Note:

Which royal blue tube should I use?

Specimen Minimum Volume

0.3 mL

Specimen Stability Information

Specimen Type Temperature Time
Metal Free EDTA Plasma Refrigerated (preferred) 5 days
  Ambient  72 hours
RBCS Refrigerated (preferred) 5 days
  Ambient  72 hours

Reject Due To


Mild reject; Gross reject








All other collection tubes except Royal blue-top metal free EDTA

Reference Values

3.5 - 7.1 mg/dL

Method Name

Inductively Coupled Plasma/Mass Spectrometry (ICP-MS)

Day(s) and Time(s) Performed

Monday through Sunday

Analytic Time

3 days

LOINC Code Information

Test ID Test Order Name Order LOINC Value
FMAGR Magnesium, RBC In Process


Result ID Test Result Name Result LOINC Value
Z4363 Magnesium, RBC 26746-8
Z4364 Magnesium, Plasma 19123-9

CPT Code Information


Profile Information

Test ID Reporting Name Available Separately Always Performed
Z4363 Magnesium, RBC No Yes
Z4364 Magnesium, Plasma No No
Laboratory Test Directory Additional Information:

Which royal blue tube should I use?