Lab Test



Test Codes




Specimen Collection Criteria


Preferred Sample:  One Light Green (Mint) Top Plasma Separator Tube (PST). (Minimum Whole Blood: 4.0 mL) 

Acceptable Sample:  One Gold Top SST (Minimum Whole Blood: 4.0 mL) 

Do NOT use Dark Green-top Lithium or Sodium Heparin tubes.


COLLECT:  One Gold Top SST (Minimum Whole Blood:  4.0 mL) 

Contact Laboratory for acceptability of other tube types.
See Minimum Pediatric Specimen Requirements for Microtainer® collection.

Physician Office/Draw Specimen Preparation

Let SST specimens clot 30-60 minutes then immediately centrifuge to separate serum from cells. Refrigerate (2-8°C or 36-46°F) the centrifuged SST tube within two hours of collection. (Minimum: 0.5 mL)

Preparation for Courier Transport

Transport: Centrifuged SST tube, refrigerated (2-8°C or 36-46°F). (Minimum: 0.5 mL)

Rejection Criteria

Moderate to grossly hemolyzed specimens.

Red-top tubes with serum not separated from cells within two hours of collection.

In-Lab Processing

Let SST specimens clot 30-60 minutes. Centrifuge SST tubes and Microtainers® to separate serum from cells. Deliver immediately to the appropriate testing station.


Specimen Stability for Testing:

Centrifuged SST Tubes and Microtainers® with Separator Gel
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

Red-top Tubes and Microtainers® without Separator Gel
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
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): 7 days

Specimen Storage in Department Prior to Disposal:

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


Canton Chemistry Laboratory
Dearborn Chemistry Laboratory
Farmington Hills Chemistry Laboratory
Grosse Pointe Chemistry Laboratory
Livonia Main Laboratory
Lenox Main Laboratory
Royal Oak Automated Chemistry Laboratory
Troy Chemistry Laboratory
Taylor Chemistry Laboratory
Trenton Chemistry Laboratory
Wayne Chemistry Laboratory 


Sunday – Saturday, 24 hours a day.
STAT results available within 1 hour of receipt in the Laboratory.
Routine results available within 4 hours.

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
2 years - 12 years 138-145
13 years - adult 135-145

Test Methodology



  • Hypernatremia (increased sodium) occurs in dehydration, diarrhea, with osmotic diuretics, diabetes mellitus, obstructive uropathy, or renal dysplasia. Hypernatremia may also result from sodium excess due to excess sodium bicarbonate, hypertonic IV fluids, sodium chloride tablets, ingestion of sea water, improperly mixed formula, primary or secondary aldosteronism or Cushing's syndrome.
  • Hypernatremia without obvious cause may relate to Cushing's syndrome, central or nephrogenic diabetes insipidus with insufficient fluids, primary aldosteronism, and other diseases. Severe hypernatremia may be associated with volume contraction, lactic acidosis, azotemia, weight loss, and increased hematocrit as evidence of dehydration.
  • A common cause of hypernatremia in pediatric cases is enteric disease which can produce hypernatremic dehydration secondary to diarrhea, vomiting, anorexia and failure of water intake.
  • Hyponatremia (decreased sodium) occurs with nephrotic syndrome, cachexia, intravenous glucose infusion, in congestive heart failure, and other clinical entities. Serum sodium is a predictor of cardiovascular mortality in patients in severe congestive heart failure. Hyponatremia also occurs as a result of water retention or sodium loss or both. Bodily depletion of sodium may be due to gastrointestinal loss, e.g., diarrhea and vomiting, diuretic therapy, sweating, hypoadrenalism or a variety of renal disorders.
  • Drug-induced hyponatremia has two usual causes- diuretic induced and ADH-like action of some drugs such as chlorpropamide and carbamazepine.
  • Hyponatremia without congestive failure or dehydration may occur with hypothyroidism, the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), renal failure, or renal sodium loss.

Clinical Utility

The quantitation of sodium is used to monitor electrolyte balance.

CPT Codes



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