Lab Test

Sodium, Direct Potentiometry, Whole Blood

NA, Sodium, Pseudohyponatremia

Test Codes





Sodium, Direct Potentiometry should ONLY be collected at the Dearborn, Grosse Pointe, Royal Oak, Taylor, Trenton, Troy, or Wayne Hospital Campuses. Specimens should not be collected at any other Beaumont Laboratory drawsite, nursing home, or Outreach office. 

Specimen Collection Criteria

Collect (preferred specimen): One Dark Green-top Lithium Heparin tube (Minimum Whole Blood: 1.0 mL). 

Also acceptable: Light Green Plasma Separator (PST) tube. 

Transport specimen STAT to the Laboratory after collection. 

Rejection Criteria

Specimen in which significant delays occur before arrival in the Laboratory (greater than 2 hours). 

Inpatient Specimen Preparation

Transport the specimen STAT to the STAT Laboratory (Royal Oak) or Chemistry Laboratory on site. 

In-Lab Processing

Immediately analyze the whole blood specimen (or plasma, after centrifugation) upon receipt in the Laboratory. 


Specimen Stability for Testing:

Dark Green-top Lithium Heparin tube
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Centrifuged PST Tube 
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours 
Refrigerated (2-8°C or 36-46°F): 7 days 
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days 


Dearborn Chemistry Laboratory
Grosse Pointe Chemistry Laboratory
Lenox Main Laboratory
Livonia Main Laboratory
Royal Oak STAT Laboratory
Taylor Chemistry Laboratory
Trenton Chemistry Laboratory
Troy Chemistry Laboratory
Wayne Chemistry Laboratory 


Sunday – Saturday, 24 hours a day.
Results available within 30 minutes of receipt in the Laboratory. 

Reference Range

Adult range: 135-145 mmol/L.
Age related reference range: 

Age Range (mmol/L) 
 0-1 Day  126 - 166
 2-29 Days  134 - 144
 30 Days - 1 Year  139 - 146
 Greater than 1 Year - 12 Years  138 - 145
 13 Years - Adult  135 - 145

Test Methodology

Direct Potentiometry. 


See Sodium

Clinical Utility

Although relatively rare, an apparent hyponatremia may be observed in some patients with extremely elevated concentrations of protein or lipids in the blood. This may occur because most automated chemistry analyzers measure the patient plasma or serum indirectly after a dilution. Patients with hyperproteinemia or hyperlipidemia will have less of the water fraction of the blood taken into the reaction vessel, causing an artifactually low sodium measurement.

Blood gas analyzers do not dilute the patient sample and directly measure the concentration of sodium ions. The sample handling is manual rather than automated, so this separate order is needed. Direct potentiometry by blood gas analyzer is also used for sodium determination in the Blood Gas, Critical Care Panel [LAB7021]. 

CPT Codes



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