Test Catalog

Test ID: NH3V    
Ammonia, Plasma

Useful For Suggests clinical disorders or settings where the test may be helpful

Assisting in the diagnosis of hepatic coma


Investigating and monitoring treatment for inborn errors of metabolism


Evaluating patients with advanced liver disease

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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 Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

< or =30 mcmol/L

Interpretation Provides information to assist in interpretation of the test results

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)

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Specimens should be put on ice immediately after collection, centrifuged at refrigerated temperature, and plasma kept on ice until analyzed.


Proper specimen handling is critical; false increases in ammonia may occur if transport and processing instructions are not strictly followed.

Clinical Reference Recommendations for in-depth reading of a clinical nature

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