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Test ID: NH3V Ammonia, Plasma

Useful For

Assisting in the diagnosis of hepatic coma


Investigating and monitoring treatment for inborn errors of metabolism


Evaluating patients with advanced liver disease

Reporting Name

Ammonia, P

Specimen Type

Plasma EDTA

Shipping Instructions

Plasma must be separated from cells and frozen within 2 hours of collection. Freeze plasma on dry ice or in a freezer (-60 to -80° C) for long-term storage or shipment.

Specimen Required

Collection Container/Tube: Lavender top (EDTA)

Submission Container/Tube: Plain, plastic screw-top tube

Specimen Volume: 0.5 mL or more

Collection Instructions:

1. Specimens should be put on ice immediately after collection.

2. Centrifuge at refrigerated temperature (4° C).

3. Aliquot plasma into plastic screw-top tube. Keep on ice.

4. Freeze plasma within 2 hours of collection.

Specimen Minimum Volume

See Specimen Collection

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma EDTA Frozen (preferred) 7 days
  Refrigerated  2 hours

Clinical Information

Ammonia is a waste product of protein catabolism; it is potentially toxic to the central nervous system. Increased plasma ammonia may be indicative of hepatic encephalopathy, hepatic coma in terminal stages of liver cirrhosis, hepatic failure, acute and subacute liver necrosis, and Reye's syndrome. Hyperammonemia may also be found with increasing dietary protein intake.


The major cause of hyperammonemia in infants includes inherited deficiencies of urea cycle enzymes, inherited metabolic disorders of organic acids and the dibasic amino acids lysine and ornithine, and severe liver disease.

Reference Values

≤30 mcmol/L


Plasma ammonia concentrations do not correlate well with the degree of hepatic encephalopathy.


Elevated ammonia concentration may also be found with increased dietary protein intake.


Plasma ammonia concentrations in newborns younger than one week are elevated compared to adults. Values less than or equal to 82 mcmol/L have been observed.(1)

Clinical Reference

1. Madigan T, Block DR, Carey WA, et al: Proposed plasma ammonia reference intervals in a reference group of hospitalized term and preterm neonates. J App Lab Med. 2020 Mar 1;5(2):363-369

2. Rosenberg W: Liver disease. In: Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:1348-1397

Day(s) and Time(s) Performed

Monday through Sunday; Continuously

Analytic Time

Same day/1 day

Test Classification

This test has been cleared, approved or is exempt by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
NH3V Ammonia, P 16362-6


Result ID Test Result Name Result LOINC Value
NH3V Ammonia, P 16362-6

Method Name

Photometric, Bromophenol Blue

Mayo Clinic Laboratories | Gastroenterology Catalog Additional Information: