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Test Code Billings Clinic: 4071 Magnesium, Plasma or Serum

Performing Laboratory

Billings Clinic Laboratory:  Chemistry

Useful For

Magnesium levels may be used to monitor 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.

Methodology

Colorimetric Xylidyl Blue

Specimen Requirements

Submit only 1 of the following specimens:

Serum or plasma should be physically separated from cells as soon as possible with a maximum limit of two hours from the time of collection.

Plasma

  • Draw blood in a green-top (lithium heparin) tube(s).
  • Spin down and send 1.0 mL of heparinized plasma frozen.

 

Serum

  • Draw blood in a plain, red-top tube(s) or a serum gel tube(s).
  • Spin down and send 1.0 mL of serum frozen

Storage/Stability

Specimen Type Temperature Time
Plasma, Serum Refrigerated 7 days
  Frozen (preferred) 1 year

 

Reject Due To

  • Hemolysis
  • Specimens collected in EDTA
  • Icterus

Reference Values

Reference Range:

0 - 12 years: 1.6 - 2.5 mg/dL

> 12 years: 1.6 - 2.6 mg/dL

 

Critical Values:

Low:    ≤ 1.0 mg/dL

High:    >8.5 mg/dL

Day(s) Test Set Up

Daily

Test Classification and CPT Coding

83735 - Magnesium

LOINC Code Information

Reporting Name LOINC Code
Magnesium 19123-9

 

Interferences

  • Hemoglobin concentrations above 500 mg/dL may result in a positive bias in serum/plasma specimens. Hemoglobin at 750 mg/dL increases the magnesium result in serum/plasma at 1.60 mg/dL by 13%.
  • Unconjugated bilirubin concentrations above 15 mg/dL may result in a positive bias in urine specimens. Unconjugated bilirubin at 30 mg/dL increases the magnesium result in urine at 2.00 mg/dL by 11%.
  • EDTA concentrations above 12.5 mg/dL may result in a negative bias in serum/plasma specimens. EDTA at 25 mg/dL decreases the magnesium result in serum/plasma at 1.60 mg/dL and 2.60 mg/dL by -15%.
  • Zinc concentrations above 0.25 mg/dL may result in a positive bias in serum/plasma specimens. Zinc at 0.5 mg/dL increases the magnesium result in serum/plasma at 1.60 mg/dL by 19%. Zinc at 0.5 mg/dL increases the magnesium result in serum/plasma at 2.60 mg/dL by 14%.