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Epic Code LAB3400 Discontinued: OB Magnesium, Blood Level

Important Note

This test will be discontinued on 3/17/2024. Replacement test MAGNESIUM [LAB103] OEE

Test Name Alias

OB Magnesium Blood Level, OB Mg Blood Level, obstetric | 365

Interface Order Alias


Ordering Instructions

This test is limited to hospital obstetrical patients that have been administered intravenous magnesium sulfate.

This test is only for Obstectric (OBGYN) Patients.

This test can no longer be added on to specimens in lab.

Collection Instructions

Specimen Collection: Blood


Container(s): 4.5 mL Mint Green Top (Lithium Heparin Gel) or 5.0 mL Gold Top (Serum Separator-SST Gel)

Preferred Volume to Collect: 4.5 mL

Minimum Volume to Collect: 1.0 mL

Neonate Volume to Collect: Not applicable

Capillary collect ok? Yes

Microtainer acceptable: Yes


Collection Instructions:

  • This test is only for Obstectric (OBGYN) Patients.

  • After collection, gently invert tube 8-10 times.
  • Specimen should be processed within 2 hours – See Processing Instructions.

Processing Instructions (Laboratory, Outpatient or Off-site collection)

Processed Specimen: Plasma or Serum

Centrifuge/Spin: Yes

Aliquot: Yes


Processing Instructions:

  • Plasma is preferred specimen type
  • Green Tube/Plasma: Centrifuge after collection within 2 hours.
  • Gold Tube/Serum: Allow blood to clot for 30 minutes in a vertical position and centrifuge within 1 hour.

Transport Temperature: Refrigerate

Specimen Transport Temperature


Specimen Stability

This test can no longer be added on to specimens in lab.

Ambient: 8 hours

Refrigerate: 72 hours

Frozen: aliquot plasma/serum for longer storage

Laboratory Retention: 72 hours

Test Frequency

Available 24 hours, usual TAT 1 day.

Reference Range

4.8 – 8.0 mg/dL Therapeutic

8.0 – 12.0 mg/dL Loss of Deep Tendon Reflexes

10.0 – 12.0 mg/dL Somnolence

12.0 -16.0 mg/dL Respiratory difficulty/depression

15.0 -17.0 mg/dL muscular paralysis

> 18.0 mg/dL altered cardiac conduction


Laboratory Critical Values Table

Performing Department


Performing Department Laboratory Location

Corewell Health Reference Laboratory, Grand Rapids, MI
Corewell Health Big Rapids Laboratory, Big Rapids, MI
Corewell Health Blodgett Laboratory, Grand Rapids, MI
Corewell Health Gerber Laboratory, Fremont, MI
Corewell Health Kelsey Laboratory, Lakeview, MI
Corewell Health Ludington Laboratory, Ludington, MI
Corewell Health Pennock Laboratory, Hastings, MI
Corewell Health Reed City Laboratory, Reed City, MI
Corewell Health Greenville Laboratory, Greenville, MI
Corewell Health Zeeland Laboratory, Zeeland, MI





CDM Code


Epic Test ID


Additional Information

PolicyTech Procedure Reference #8530: Magnesium Sulfate Infusion in the Obstetrical Patient

Reviewed Date