Ordering Recommendation

May be useful in the assessment of tissue stores. For routine assessment of magnesium deficiency, Magnesium, Plasma or Serum (0020039) is preferred.

New York DOH Approval Status

This test is New York state approved.

Specimen Required

Patient Preparation

Royal blue (K2EDTA) or Royal blue (NaHep).

Specimen Preparation

Centrifuge whole blood and separate RBCs from plasma within 2 hours of collection. Submit packed RBCs in original tube OR transfer 2 mL RBCs to an ARUP Trace Element-Free Transport Tube (ARUP supply #43116) available online through eSupply using ARUP Connect™ or contact ARUP Client Services at (800) 522-2787. (Min: 0.6 mL)

Storage/Transport Temperature

Room temperature. Also acceptable: Refrigerated.

Unacceptable Conditions

Specimens collected in tubes other than royal blue (K2EDTA) or royal blue (NaHep). Specimens transported in containers other than royal blue (K2EDTA) or royal blue (NaHep) tube or trace element-free transport tube. Clotted or grossly hemolyzed specimens.


After separation from plasma: Ambient: 2 weeks; Refrigerated: 2 weeks; Frozen: Unacceptable


Quantitative Inductively Coupled Plasma-Mass Spectrometry




1-4 days

Reference Interval

3.6-7.5 mg/dL

Interpretive Data

RBC magnesium results reflect the intracellular stores and general homeostasis of magnesium. Results may be falsely low if RBCs in the submitted specimen are lysed or not promptly separated from plasma.

RBC magnesium concentration is reported as milligrams per deciliter (mg/dL). To convert concentration to millimoles per liter (mmol/L), divide the result by 2.43.

Compliance Category

Laboratory Developed Test (LDT)


Hotline History


CPT Codes



Component Test Code* Component Chart Name LOINC
0092080 Magnesium, RBCs 26746-8
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.


  • Intracellular Magnesium
  • MgRBCs
Magnesium, RBC