Lab Test


NH3, Blood

Test Codes

Antrim #17136, EPIC: LAB5007, NH4



Specimen Collection Criteria

Collect: One Lavender-top EDTA tube. (Minimum Whole Blood: 3.0 mL)
See Minimum Pediatric Specimen Requirements for Microtainer® collection.

Collect specimen on ice. Send immediately on ice to the Laboratory for processing. Uncentrifuged specimens must be received on ice within 30 minutes after collection.

For Farmington Hills:
Both Lavender and NaHep Dark Green top tubes on ice are acceptable.

Physician Office/Draw Specimen Preparation

Do not freeze whole blood. Centrifuge immediately to separate plasma from cells. Transfer plasma to plastic transport tube and freeze (-20°C/-4°F or below) immediately. Plasma can be placed on ice for up to 2 hours. If the transport delay is anticipated to be greater than 2 hours, the plasma must be frozen (-20°C/-4°F or below). (Minimum: 1.0 mL)

Preparation for Courier Transport

Transport: Plasma in a plastic transport tube, frozen (-20°C/-4°F or below). (Minimum: 1.0 mL)

Rejection Criteria

  • Hemolyzed specimens.
  • Frozen whole blood specimens.
  • Specimens not immediately placed on ice after collection.
  • Specimens not centrifuged, transported, or stored as indicated.

Inpatient Specimen Preparation

Deliver specimen on ice to the Laboratory immediately. Specimen must be received on ice within 30 minutes after collection.

In-Lab Processing

Centrifuge immediately to separate plasma from cells. Keep sample on ice prior to analysis. Test specimen immediately.


Specimen Stability for Testing:

Room Temperature (20–26°C or 68–78.8°F): Unacceptable
Refrigerated (2–8°C or 36–46°F): 2 hours maximum (plasma only)
Frozen (-20°C/-4°F or below): 14 days (plasma only)

Specimen Storage in Department Prior to Disposal:

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


Dearborn Chemistry Laboratory
Farmington Hills Chemistry Laboratory
Grosse Pointe Chemistry Laboratory
Lenox Main Laboratory
Livonia Main Laboratory
Royal Oak STAT 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 24 hours.

Reference Range

Farmington Hills:
11 – 35 mcmol/L.

Grosse Pointe, Royal Oak & Troy:
15 – 50 mcmol/L.

Test Methodology



Elevated ammonia levels may be seen in liver disease, urinary tract infection with distention and stasis, Reye's syndrome, administration of total parenteral nutrition and in patients receiving valproic acid. It may also be elevated following gastrointestinal hemorrhage. Elevated ammonia is associated with a number of inborn errors of metabolism, including enzyme defects of the urea cycle, methylmalonic acidemia and propionic acidemia.

Clinical Utility

The diagnostic utility of ammonia measurements is limited. The test is used mainly in the diagnosis of urea cycle defects and in the detection of Reye's syndrome. Levels of ammonia do not correlate well with CNS changes in end-stage liver disease.

CPT Codes

LOINC: 16362-6


Last Updated


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